Digital

Digital

Revision: v0.30
Date: 2023-02-03 10:55

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Table of Contents
A General
1. Digital .................................................................................................................................. 6
1.1. Introduction .................................................................................................................... 6
1.2. First Steps ......................................................................................................................6
1.3. Wires ............................................................................................................................ 14
1.4. Hierarchical Design ......................................................................................................14
2. Simulation ......................................................................................................................... 18
2.1. Propagation Delay ....................................................................................................... 18
3. Analysis .............................................................................................................................18
3.1. Circuit Analysis and Synthesis .................................................................................... 18
3.2. Expression ................................................................................................................... 18
3.3. State charts ..................................................................................................................19
4. Hardware .......................................................................................................................... 19
4.1. GAL16v8 and GAL22v10 .............................................................................................19
4.2. ATF150xAS ..................................................................................................................19
4.3. Export to VHDL or Verilog ...........................................................................................19
5. Custom Shapes ................................................................................................................ 20
6. Generic Circuits ................................................................................................................ 21
7. Script-controlled testing .................................................................................................... 22
8. Frequently asked Questions .............................................................................................22
9. Keyboard Shortcuts .......................................................................................................... 24
B Settings
C Command Line Interface
D Components
1. Logic
1.1. And ..............................................................................................................................31
1.2. NAnd ........................................................................................................................... 31
1.3. Or ................................................................................................................................ 32
1.4. NOr ..............................................................................................................................33
1.5. XOr ..............................................................................................................................33
1.6. XNOr ........................................................................................................................... 34
1.7. Not ...............................................................................................................................35
1.8. Lookup Table .............................................................................................................. 35
2. IO
2.1. Output ......................................................................................................................... 36
2.2. LED ............................................................................................................................. 37
2.3. Input ............................................................................................................................ 37
2.4. Clock Input .................................................................................................................. 38
2.5. Button ..........................................................................................................................39
2.6. DIP Switch .................................................................................................................. 39
2.7. Probe ...........................................................................................................................40
2.8. Data Graph ................................................................................................................. 40
2.9. Triggered Data Graph .................................................................................................41
3. IO - Displays
3.1. RGB-LED .................................................................................................................... 41

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3.2. LED with two connections. ......................................................................................... 42

3.3. Button with LED ..........................................................................................................42
3.4. Seven-Segment Display ............................................................................................. 43
3.5. Seven-Segment Hex Display ...................................................................................... 44
3.6. 16-Segment Display ....................................................................................................44
3.7. Light Bulb ....................................................................................................................45
3.8. LED-Matrix .................................................................................................................. 45
4. IO - Mechanical
4.1. Rotary Encoder ........................................................................................................... 46
4.2. Stepper Motor, unipolar .............................................................................................. 46
4.3. Stepper Motor, bipolar ................................................................................................ 47
5. IO - Peripherals
5.1. Keyboard .....................................................................................................................48
5.2. Terminal ...................................................................................................................... 49
5.3. Telnet .......................................................................................................................... 49
5.4. VGA Monitor ............................................................................................................... 50
5.5. MIDI .............................................................................................................................51
6. Wires
6.1. Ground ........................................................................................................................ 51
6.2. Supply voltage ............................................................................................................ 52
6.3. Constant value ............................................................................................................ 52
6.4. Tunnel ......................................................................................................................... 53
6.5. Splitter/Merger .............................................................................................................53
6.6. Driver ...........................................................................................................................54
6.7. Driver, inverted select ................................................................................................. 55
6.8. Delay ........................................................................................................................... 55
6.9. Pull-Up Resistor .......................................................................................................... 56
6.10. Pull-Down Resistor ................................................................................................... 56
6.11. Not Connected .......................................................................................................... 56
7. Plexers
7.1. Multiplexer ...................................................................................................................57
7.2. Demultiplexer .............................................................................................................. 57
7.3. Decoder .......................................................................................................................58
7.4. Bit Selector ................................................................................................................. 59
7.5. Priority Encoder .......................................................................................................... 59
8. Flip-Flops
8.1. RS-Flip-flop ................................................................................................................. 60
8.2. RS-Flip-flop, clocked ...................................................................................................61
8.3. JK-Flip-flop .................................................................................................................. 62
8.4. D-Flip-flop ....................................................................................................................63
8.5. T-Flip-Flop ................................................................................................................... 63
8.6. JK-Flip-flop, asynchronous ..........................................................................................64
8.7. D-Flip-flop, asynchronous ........................................................................................... 65
8.8. Monoflop ..................................................................................................................... 66
9. Memory - RAM
9.1. RAM, separated Ports ................................................................................................ 67
9.2. Block-RAM, separated ports ....................................................................................... 68
9.3. RAM, bidirectional Port ............................................................................................... 69
9.4. RAM, Chip Select ....................................................................................................... 70
9.5. Register File ................................................................................................................71

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9.6. RAM, Dual Port ...........................................................................................................72

9.7. RAM, async. ............................................................................................................... 73
9.8. Graphic RAM .............................................................................................................. 73
10. Memory - EEPROM
10.1. EEPROM ...................................................................................................................74
10.2. EEPROM, separated Ports ....................................................................................... 75
11. Memory
11.1. Register .....................................................................................................................76
11.2. ROM ..........................................................................................................................77
11.3. ROM dual port .......................................................................................................... 78
11.4. Counter ..................................................................................................................... 79
11.5. Counter with preset ...................................................................................................80
11.6. Random Number Generator ..................................................................................... 81
12. Arithmetic
12.1. Adder .........................................................................................................................82
12.2. Subtract .....................................................................................................................82
12.3. Multiply ...................................................................................................................... 83
12.4. Division ......................................................................................................................84
12.5. Barrel shifter ..............................................................................................................84
12.6. Comparator ............................................................................................................... 85
12.7. Negation ....................................................................................................................86
12.8. Sign extender ............................................................................................................86
12.9. Bit counter .................................................................................................................87
13. Switches
13.1. Switch ........................................................................................................................87
13.2. Double Throw Switch ................................................................................................88
13.3. Relay ......................................................................................................................... 88
13.4. Double Throw Relay ................................................................................................. 89
13.5. P-Channel FET ......................................................................................................... 90
13.6. N-Channel FET ......................................................................................................... 91
13.7. Fuse .......................................................................................................................... 91
13.8. Diode to VDD ............................................................................................................92
13.9. Diode to Ground ....................................................................................................... 92
13.10. P-Channel floating gate FET .................................................................................. 93
13.11. N-Channel floating gate FET .................................................................................. 94
13.12. Transmission-Gate .................................................................................................. 94
14. Misc.
14.1. Test case .................................................................................................................. 95
15. Misc. - Decoration
15.1. Text ........................................................................................................................... 95
15.2. Rectangle .................................................................................................................. 96
16. Misc. - Generic
16.1. Generic Initialization ..................................................................................................96
16.2. Code ..........................................................................................................................97
17. Misc. - VHDL/Verilog
17.1. External ..................................................................................................................... 97
17.2. External File .............................................................................................................. 98
17.3. Pin Control ................................................................................................................ 99
18. Misc.
18.1. Power ........................................................................................................................ 99

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18.2. Bidirectional Splitter ................................................................................................ 100

18.3. Reset .......................................................................................................................100
18.4. Break .......................................................................................................................101
18.5. Stop .........................................................................................................................101
18.6. Asynchronous Timing ............................................................................................. 102
E Library

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A General
1. Digital
1.1. Introduction

Digital is a simple simulator used to simulate digital circuits. The logic gates are connected
to each other by wires and the behavior of the overall circuit can be simulated. The user can
interact with the simulation by either pressing buttons or setting values to the inputs of the
circuit.
In this way, most of the basic circuits used in digital electronics can be built and simulated. In the
folder examples, users can browse for examples that includes a functional 16-bit single-cycle
Harvard processor.
The simulator has two modes of operation: Editing and Simulation mode. In the editing mode,
modifications to the circuit can be performed. Users can add or connect components. In this
mode, simulation is disabled. The simulation mode is activated by pressing the Start button
in the toolbar. While starting the simulation the circuit is checked for consistency. If there are
errors in the circuit an appropriate message is shown and the affected components or wires
are highlighted. If the circuit is error free, the simulation is enabled. Now you can interact with
the running simulation. In the simulation mode it is not possible to modify the circuit. To do so
you have to activate the editing mode again by stopping the simulation.

1.2. First Steps

As a first example, a circuit is to be constructed with an Exclusive-Or gate. From the main
window, the Components menu allows you to select the various components. Then they are
placed on the drawing panel. This process can be canceled by pressing the ESC key at any
time. Start by selecting an input component. This can later be controlled interactively by using
the mouse.

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After selection, the first input can be placed on the drawing panel. The red dot on the input
component symbol is a connection point between the component and a wire, which will be
connected later on. The red color indicates an output. This means that the port defines a signal
value or can drive a wire.

In the same way, a second input is added. It is best to place it directly below the first input.

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After adding the inputs, the Exclusive-Or gate is selected. This gate represents the actual logical
function.

This gate can now also be added to the circuit. It is best to place it in a way that the subsequent
wiring is made as simple as possible. The blue dots indicate the input terminals of the gate.

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Now, select an output which could be used to display a signal state or to later pass signals
to an embedding circuit.

This is placed in a way that it can be wired easily. The output has a blue dot, which indicates
an input terminal. Here you can feed in the value which is then exported.

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After all components are selected and in place, use the mouse to wire a connection between
the blue and red dots. Make sure that exactly one red dot is connected to any number of blue
dots. Only the usage of three-state outputs makes it possible to deviate from this rule and to
interconnect several red dots. If all wires have been drawn, the circuit is complete.

Interaction with the circuit is possible when simulation is started. This is done by clicking on the
play button located in the toolbar. After starting the simulation, the color of the wires changes
and the inputs and outputs are now filled. Bright green indicates a logical '1' and dark green a
logical '0'. In the figure above, all wires have a '0' value.

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By clicking with the mouse, the inputs can be switched. Since the simulation is now active, the
output changes according to the current input states. The circuit behaves like an Exclusive-Or
gate as expected .

To further process the circuit, the simulation must first be stopped. The easiest way to do this
is with the Stop button in the tool bar. Clicking on a component with the right mouse button
(control-click on macOS) opens a dialog which shows the component's properties. The label
'A' can be defined for the first input via this dialog.

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In the same way, the labels for the remaining inputs and outputs can be defined. The menu
item Analysis also contains a menu item Analysis. This function performs an analysis of the
current circuit. However, this is only possible if all inputs and outputs are labeled properly.

The truth table of the simulated circuit appears in a new window. Below the table you can
find the algebraic expression associated with the circuit. If there are several possible algebraic
expressions, a separate window will open, showing all possible expressions.

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The table dialog has the menu entry K-Map in its main menu. This allows to display the truth
table in the form of a K-map.

At the top of this dialog there is a drop-down list which allows the selection of the desired ex-
pression in the K-map. In this way you can, for example, illustrate how several equivalent alge-
braic expressions can result. However, in this example, there is only one minimal expression.
The truth table can also be modified by clicking the K-map.

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1.3. Wires

All components must be connected via wires. It is not possible to connect two components by
placing them directly next to each other.
In addition, there are only connections between an endpoint of a wire and a component. If
a pin of a component is placed in the middle of a wire, no connection is made between the
component and the wire. Therefore, a wire must actually terminate at each pin which is to be
connected. Even if the tunnel component is used, there must be a wire between the pin and
the tunnel element.
The component needs to be selected using the rectangular selection tool in order to be moved
along with the connected wires. For moving a component without the connected wires, select
the component using a mouse click.
With CTRL-Click a single wire section can be selected to move or delete it. If the D key is
pressed while drawing a wire, a diagonal wire can be drawn. The key S allows the splitting of
a line segment into two segments.

1.4. Hierarchical Design

If a complex circuit is built up, this can quickly become very confusing. To keep track here,
the different parts of a circuit can be stored in different files. This mechanism also makes it
possible to use a subcircuit, which has been created once, several times in a further circuit.
This approach also offers the advantage that the files can be stored independently of each
other in a version control system and changes can be tracked.

As an example, consider a 4-bit adder: First, we built a simple half-adder. This consists of an
XOR gate and an AND gate. The sum of the two bits 'A' and 'B' is given to the outputs 'S' and
'C'. This circuit is stored in the file halfAdder.dig.

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From two half adders a full adder can now be built. To do this, create a new empty file and
save the empty file as fullAdder.dig in the same folder as the half adder. Then the half adder
can be added to the new circuit via the Components →Custom menu. The order of the pins at
the package of the half-adder can be rearranged from the half adder in the menu Edit →Order
inputs or Edit →Order outputs. The full adder adds the three bits 'A', 'B' and 'Ci' and gives the
sum to the outputs 'S' and 'Co'.

In order to check the correct function of the full adder, a test case should be added. In the test
case, the truth table is stored, which should fulfill the circuit. In this way it can be automatically
checked whether this is the case.

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The tests can be executed via the test case editor or the test button in the toolbar. The table
cells highlighted in green indicate that the output of the circuit matches the truth table given
in the test case.

Now the full adders can be put together to form a so-called ripple-carry adder. In this case, the
carry output of an addition is forwarded as a carry input to the addition of the next higher-order
bit, just as is usual in pencil-and-paper addition. This 4-bit adder should be tested for correct
function. For this purpose a test case was inserted.

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This test case performs a 100% test, which is possible only with relatively simple circuits: all
possible 512 input combinations are applied to the circuit, and it is checked whether the output
of the circuit is correct. The first line lists the input and output signals. Below this, the input
values to be applied and the output values to be checked are specified in a row, as in a truth
table. In this example, however, 512 lines are required. Entering this would be a tedious and
error-prone task. It is easier and more reliable to automatically generate the required lines. For
this purpose, the variables A and B are each traversed from 0 to 15. The respective values
of A and B are then assigned to inputs 'A[n]' and 'B[n]'. Then it is checked whether the circuit
outputs the value A+B. Then it is checked again with the carry bit set, in which case A+B+1
must result. The details of the test syntax are provided by the help dialog.
If a circuit is embedded in an other circuit, only the file name of the subcircuit is stored in a cir-
cuit, not the embedded circuit itself. The corresponding files of the embedded subcircuits must
therefore be found in the file system at runtime of the simulation. In order to support the various
work methods of the users as best as possible and still to avoid a complex administration of
import paths, etc., a somewhat unusual import strategy is implemented.
Only the file names of the embedded circuits are stored in a circuits file, not the full path. If a
file needs to be opened, all subfolders are searched for a file of the corresponding name. If a
suitable file is found, it is imported. This process only depends on the file name of the file to be
read, not on its path. Correspondingly, an error message is generated if there are several files
of the same name in different subfolders, since ambiguities then arise.
A suitable project structure therefore looks as follows: The root circuit is located in a separate
folder. All imported circuits must be in the same folder or subfolders. All circuits must have
different names, so it must not happen that there are circuits of the same name in different
folders.

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2. Simulation
2.1. Propagation Delay

During the simulation every logic gate has a propagation delay. Every component found in the
library has the same propagation delay regardless of its complexity. The AND gate thus has
the same propagation delay as the multiplier. The only exceptions are diodes, switches and
splitters which are used to create data buses. These components have no propagation delay
at all.
If it's necessary to simulate a gate - e.g. the multiplier - with a longer propagation delay, a delay
gate must be inserted in the circuit right behind the output of the multiplier.
If a circuit is included in another parent circuit, the included circuit keeps its timing behaviour. So
if you include a complex circuit which has a large propagation delay because the input signals
has to pass three gates until it reaches the output, this behaviour is conserved while including
this circuit. There are no additional delays introduced as a result of including a circuit. If not all
outputs of a circuit have the same propagation delay, then this is also the case if it is included
in a parent circuit. In general, including a circuit into an other circuit does not modify its timing
behaviour at all. An included circuit behaves exactly the same way as if all components had
been inserted at the same circuit level.

3. Analysis
3.1. Circuit Analysis and Synthesis

A circuit can be analyzed via the menu entry Analysis. A truth table is generated for purely
combinatorial circuits. This truth table can be edited as desired. A new circuit can be generated
from this truth table after editing.
In addition to purely combinatorial circuits, it is also possible to analyze or generate sequential
circuits. Instead of a simple truth table a so-called state transition table is created. Each flip-
flop thereby appears on the input side and the output side of the state transition table. In this
table, on the right-hand side, you can find the next state, which will occur after the next clock
signal. This next state depends on the current state of the flip-flops as found at the left-hand
side of the table. For an analysis to be possible, the flip-flops must be named.
The following naming convention applies: The following next state of a bit on the right side
of the table is indicated by a lowercase 'n+1'. The corresponding current state is indicated
by an appended 'n'. If there is a state variable 'A', 'An' indicates the current state and 'An+1'
indicates the next state. If, in the truth table on the left and right side, signals are present, which
correspond to this pattern it is assumed that the table is a state transition table, and a sequential
circuit is generated instead of a combinatorial circuit.
It should be noted that the circuit to be analyzed may contain only purely combinatorial elements
in addition to the built-in D and JK flip-flops. If a flip-flop is e.g. made from Nor gates, this circuit
is not recognized as a flip-flop and therefore it is not possible to analyse such a circuit.

3.2. Expression

Via the menu item Expression it is possible to enter a boolean function from which a circuit
can then be generated.

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3.3. State charts

An editor for state charts is available via the menu item Finite State Machine. It allows the
graphical creation of state machines by drawing states and state transitions. Thereby different
outputs can be set in the different states. By providing transitions with conditions, input signals
can be generated. By setting output values at transitions, Mealy automata can also be defined.
The state machine defined in this way can then be automatically transferred to a state transition
table, from which, in a further step, a circuit implementing the initial state machine can be
generated. If the simulation of this circuit is then started, the current state can also be followed
in the state chart.

4. Hardware
4.1. GAL16v8 and GAL22v10

In the circuit generation menu in the truth table there are also functions to generate so-called
JEDEC files. This is a special file format that describes the fuse map of a PLD. This JEDEC file
can be written into a corresponding PLD using a special programmer. At the moment, circuits
of the type GAL16v8 and GAL22v10 or fuse map compatible devices are supported.

4.2. ATF150xAS

The chips in the ATF150x family are simple CPLDs with up to 128 macrocells. They are
available in a PLCC package, which makes them suitable for laboratory exercises: If an IC is
destroyed during exercises, it can simply be replaced. In addition, with the ATDH1150USB an
easy to use, low-cost programmer is available. This programmer is able to program the AT-
F150x chips in system using a JTAG interface. A suitable evaluation board (ATF15XX-DK3-U)
is also available. The software ATMISP , which is available on the ATMEL/Microchip website,
is required for programming the chips.
Unfortunately, the fuse map details are not publicly available so that no suitable fitter for this
chip can be integrated in Digital, as is possible with the GAL16v8 and GAL22v10 chips.
Therefore, the fitters fit150[x].exe provided by ATMEL must be used. These programs create a
JEDEC file from a suitable TT2 file which can then be programmed on the chip. Digital starts the
fitter automatically every time a TT2 file is created. For this purpose, the path to the fit150[n].exe
fitters must be specified in the settings. The created JEDEC file can then be opened and pro-
grammed directly with ATMISP .
For legal reasons the fitter fit1502.exe can not be distributed with Digital. However, it can be
found in the folder WinCupl\Fitters after installing WinCupl . WinCupl is available on the
ATMEL/Microchip website. On Linux systems, the fitters can also be executed by Digital if wine
is installed.

4.3. Export to VHDL or Verilog

A circuit can be exported to VHDL or Verilog. A file is generated which contains the complete
description of the circuit. The generated VHDL code was tested with Xilinx Vivado and the
open source VHDL simulator ghdl. The Verilog code is tested with the Verilog simulator Icarus
Verilog.
If a circuit contains test cases, the test data is used to generate a HDL test bench. This can be
used to check the correct function of the circuit in a HDL simulation.

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Additional files which are needed by special boards can be created. At present only the
BASYS3 board and the Mimas boards Mimas and Mimas V2 are supported. A constraints file
is created, which contains the assignment of the pins. The description of the pins can be found
in the boards data sheet, and must be entered as a pin number for the inputs and outputs.
For a BASYS3 board, if the circuit clock frequency is low, a frequency divider is integrated
into the HDL code to divide the board clock accordingly. If the clock frequency selected in
the circuit exceeds 4.7MHz, the MMCM unit of the Artix-7 is used for clock generation. This
ensures that the FPGA resources provided for the clock distribution are used. This allows the
included example processor to run at 20MHz, and if you can do without the multiplier, 30HMz
is also possible.
If a circuit is to run on a BASYS3 board, a new project can be created in Vivado. The generated
VHDL file and the constraints file must be added to the project. Once the project has been
created, the bitstream can be generated and the Hardware-Manager can be used to program
a BASYS3 board.
In order to create the required constraints file in addition to the HDL file, the corresponding
board must be configured in the settings. In the field "Toolchain Configuration" the correspond-
ing XML file can be selected. The available configurations can be found in the folder exam-
ples/hdl and have the file extension .config. If the configuration was successfully integrated, a
further menu appears, which makes the board specific functions accessible.

5. Custom Shapes
Although Digital has some options that determine the appearance of a circuit when it is em-
bedded in another, in some cases it may be useful to use a very special shape for a subcircuit.
An example is the representation of the ALU in the processor included in the examples. This
chapter explains how to define such a special shape for a circuit.
Digital does not provide an editor for creating a special shape. Instead, a small detour is re-
quired for creating circuit shapes: First, the circuit which is to be represented by a special shape
is opened. Then an SVG template is created for this circuit. In this template, the circuit is rep-
resented by a simple rectangle. It also contains all the pins of the circuit, represented by blue
(inputs) and red (outputs) circles. To see which circle belongs to which pin, you can look at the
ID of the circle in the object properties. This ID has the form pin:[name] or pin+:[name]. In the
latter variant, the pin is provided with a label if reimported to digital. If you do not want such
a label, the + can be removed.
This SVG file can now be edited. The most suitable is the open source program Inkscape which
is available for free. The pins can be moved freely, but are moved to the next grid point during
the reimport.
If existing SVG files are to be used, it is easiest to open the created template and paste the
existing graphic into the template via Copy&Paste.
If the file was saved, it can be imported with Digital. The file is read in and all necessary infor-
mation is extracted and stored in the circuit. For further use of the circuit, the SVG file is no
longer required.
A final remark: SVG is a very powerful and flexible file format. It can be used to describe ex-
tremely complex graphics. The Digital importer is not able to import all possible SVG files with-
out errors. If a file can not be imported, or does not appear as expected, some experimentation
may be required before the desired result is achieved.

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6. Generic Circuits
It happens that a subcircuit has been created, and is to be used in different variants. For ex-
ample, you can imagine a special counter that is needed for different bit widths. If one would
create a subcircuit for 4, 5 and 6 bits each, the maintenance of the circuit would be difficult in
the future, since one must always work on several subcircuits, which are identical except for
one parameter, the bit width.
To prevent this, a generic subcircuit which can be parameterized can be created. For this
purpose, the checkbox "Circuit is generic" must be set in the circuit specific settings. Then
the parameter dialog of each component in that circuit contains the additional field "generic
parameterization". In this field program code can be entered, which can change the parameters
of the component. Each parameter has a name and can be modified as an attribute of the field
this. The names of the parameters can be found in the help dialog of the component. If you
want to change the bit width of an adder, the line this.Bits=1; can be used.
In this way, however, it is not yet possible to create a circuit that can be parameterized. It is still
necessary to access parameters that are set when the circuit is used. This is done via the field
"args". If you want to set the bit width from outside, you can write: this.Bits=args.bitWidth;. The
name of the argument - here bitWidth is arbitrary. If such a subcircuit is used, this argument
must be set.
If the circuit is used and the parameter dialog of the embedded circuit is opened, it also has a
field "generic parameterization". Here the bit width to be used can be set with the instruction
bitWidth:=5;.
If a generic circuit is to be started directly, this is not possible straight away, since the required
arguments are missing, which have to be specified when embedding the circuit. These missing
arguments would lead to corresponding error messages. Therefore, to simplify the testing of
the circuit, the Generic Initialization component can be added to the circuit. In this component
you can set the arguments that would come from an embedding circuit. In this way, a generic
circuit can also be simulated directly. If the circuit is embedded, this component is ignored. It
is only needed for the direct start of the simulation.
Under certain circumstances it may be useful not only to change the attributes of the compo-
nents of a circuit, but to add completely new components and wires depending on the passed
arguments. The Code component can be used for this purpose. If it is added to the circuit, the
contained Code will be executed when the simulation is started. Here, a wire can be added us-
ing the addWire([x1],[y1],[x2],[y2]) function, and using the function addComponent([name],[x],
[y]) a new component [name] can be added at the position ([x],[y]). The return value of the
addComponent([Name],[x],[y]) function allows to set the parameters of the component.
The example circuit examples/generic/modify/Conway/GenericConway.dig shows how a more
complex circuit can be assembled in this way.
Another way to create a circuit is recursion: it is possible, depending on the arguments, to
replace one circuit by another. For this purpose the function setCircuit([Name]) is available. If it
is called in the definition part of a subcircuit, the circuit to be inserted can be replaced by another
circuit. This allows the recursive definition of a circuit. As in other programming languages, a
suitable termination condition must be ensured.
The examples/generic folder contains an example of a Gray code counter whose bit width can
be configured. Here a Gray code counter is constructed by recursively adding further bits to an
initial circuit until the required number of bits of the counter is reached.

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7. Script-controlled testing
If students are to complete exercises with Digital, it can be helpful if the circuits submitted by
the students can be checked in an automatic process. To perform this check, Digital can be
started from the command line. The call is done as follows:
java -cp Digital.jar CLI test [file to test] [-tests [optional file
with test cases]]
If only the file to be tested is specified, the test cases in that file are executed. In this way, the
test cases created by the students themselves can be executed.
If a second file name is specified, the test cases are taken from the second file and the first
circuit is checked with these test cases. The second file will therefore usually contain the sample
solution whose test cases are complete and correct. The circuit contained in the second file is
ignored. Only the test cases are taken from it.
In order to test a submitted circuit against a sample solution, the signal names of the inputs
and outputs in both circuits must match.

8. Frequently asked Questions

How to move a wire?
Select one of the end points with the rectangular selection. Then move this point using the
mouse. You can also select a wire with CTRL + mouse button.
How to delete a wire?
Select one of the end points and press DEL or click on the trashcan. You can also select a
wire with CTRL + mouse button.
How to move a component including all the connected wires?
Select the component with the rectangular selection. The selection must include the entire
component. Then move the component including the wires using the mouse.
There is a component not connected to a wire, even though the pins are on the wire.
A pin is only connected to a wire if the wire has an endpoint at the pin.
If the names of the pins in a circuit are long, the names are no longer readable when
the circuit is embedded. What can I do?
The width of the block can be increased using the menu item Edit →Circuit specific
settings.
The pins in an embedded circuit have an non-optimal order. How can this be
changed?
The sequence can be changed using the menu entry Edit →Order inputs or Edit →Order
outputs.
When the simulation is started, a wire becomes gray. What does that mean?
The colors light green and dark green are used to represent high and low state. Gray
means the wire is in high Z state.

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I have a truth table. How to calculate the minimized boolean equations?

In the menu Analysis select the entry Synthesise. Then enter the truth table. At the bottom
of the window you can find the matching boolean equation. If you enter more than one
dependent variable, a new window opens in which all boolean equations are shown.
I have entered a truth table, but there is more than one boolean equation shown.
Which of them is the correct one?
Minimizing a boolean equation can result in many equations describing the same
function. Digital shows all of them and they all create the same truth table. There may be
differences depending on the "don't cares" in the truth table.
I have a truth table. How to create a circuit representing the truth table?
In the menu Analysis select the entry Synthesise. Then enter the truth table. You can edit
the table using the New or Edit menus. In the menu Create, you can create a circuit using
the Circuit item.
How to edit a signal's name in the truth table?
Right click on the name in the table header to edit the name.
I have a boolean equation. How to create a circuit?
In the menu Analysis select the entry Expression. Then enter the equation.
How to create a truth table from a boolean equation?
In the menu Analysis select the entry Expression. Then enter the expression. Then create
a circuit and in the menu Analysis use the entry Analysis to create the truth table.
How to create a JEDEC file from a given circuit?
In the menu Analysis select the entry Analysis. Then in the menu Create in the new
window choose the correct device in the sub menu Device.
When creating a JEDEC file: How to assign a pin number to a certain signal?
At the corresponding inputs and outputs you can enter a pin number in the settings dialog
of the pin.
I have created a JEDEC file. How to program it to a GAL16v8 or GAL22v10?
To program such a chip a special programmer hardware is necessary.
I have created a circuit that I want to use in many other circuits. How can I do this
without copying the file over and over again into the appropriate folders?
The circuit can be saved in the "lib" folder. Then it is available in all other circuits.

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9. Keyboard Shortcuts

Space Starts or stops the simulation.

F6 Opens the measurement table dialog.
F7 Run to Break.
F8 Execute test cases.
C A single clock step (Works only in a running simulation and only if there is a
single clock component).
V Execute a single gate step.
B Execute all single gate steps until the circuit has stabilized or, if a break
component is present, until the break.
F9 Analysis of the circuit.
CTRL-A Select all.
CTRL-X Cuts the selected components to the clipboard.
CTRL-C Copys the selected components to the clipboard.
CTRL-V Inserts the components from the clipboard.
CTRL-D Duplicate the current selection without modifying the clipboard.
R While inserting this rotates the components.
L Inserts the last inserted component again.
T Inserts a new tunnel.
CTRL-N New circuit.
CTRL-O Open circuit.
CTRL-S Save the circuit.
CTRL-Z Undo last modification.
CTRL-Y Redo the last undone modification.
P Programs a diode or a FGFET.
D While drawing a wire switches to the diagonal mode.
F While drawing a line flips the orientation.
S Splits a single wire into two wires.
Q Copy the component the mouse pointer is hovering over.
CTRL-Q Copy the component the mouse pointer is hovering over with default
settings.
ESC Abort the current action.
Del Removes the selected components.
Backspace Removes the selected components.

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+ Increases the number of inputs at the component the mouse points to. If it
is used with constants, the value is increased.
- Decreases the number of inputs at the component the mouse points to. If it
is used with constants, the value is decreased.
CTRL + Zoom In.
CTRL - Zoom Out.
F1 Fit to size.
F5 Show or hide the components tree view.

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B Settings
The following describes the available settings of the simulator.

Settings

The global settings of the simulator specify, among other things, the language, the symbol
form to be used or the paths of external tools.
Attributes
Use IEEE 91-1984 shapes
Use IEEE 91-1984 shapes instead of rectangular shapes
Language
Language of the GUI. Will only take effect after a restart.
Format
Screen format of expressions.
Color scheme
Color scheme
User Defined Colors
User Defined Colors
Component tree view is visible at startup.
If set, the component tree view is enabled at startup.
Show Grid
Shows a grid in the main window.
Show the number of wires on a bus.
CAUTION: The value is only updated when the simulation starts.
Wire tool tips
If set, lines are highlighted when the mouse hovers over them.
Use Equals-Key
Use the equal key instead of the plus key. This is always useful if the plus character
is not a primary key, but the second assignment of the equals character, e.g. for an
American or French keyboard layout.
Show dialog for automatic renaming of tunnels.
If set, a dialog for automatically renaming all tunnels of the same name is displayed
after a tunnel has been renamed.
Library
Folder which contains the library with predefined sub circuits. Contains, for example,
the components of the 74xx series. You also can add your own circuits by storing
them at this location. It must be ensured that the names of all files in this folder and all
subfolders are unique.
Java library
A jar file containing additional components implemented in Java.
ATF15xx Fitter
Path to the fitter for the ATF15xx. Enter the directory which contains the fit15xx.exe
files provided by Microchip (former ATMEL).
ATMISP
Path to the executable file ATMISP.exe. If set, the ATMISP software can be started
automatically!

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GHDL
Path to the executable ghdl file. Only necessary if you want to use ghdl to simulate
components defined with VHDL.
IVerilog
Path to the Icarus Verilog installation folder. Only necessary if you want to use iverilog
to simulate components defined with Verilog.
Toolchain Configuration
Used to configurate an integration of a toolchain. Allows the start of external tools, e.g.
to program an FPGA or similar.
Menus Font Size [%]
Size of the fonts used in the menu in percent of the default size.
Use macOS mouse clicks.
Uses CTRL-click instead of right-click.
Allow remote connection
If set, a TCP/IP port is opened, through which the control of the simulator is possible.
Port number
The port on which the remote server is opened.

Circuit specific settings

The circuit specific settings affect the behavior of the currently open circuit. For example, the
shape that represents the circuit when it is embedded in other circuits. These settings are
stored together with the circuit.
Attributes
Label
The name of this element.
Width
Width of symbol if this circuit is used as an component in an other circuit.
Background color
Background color of the circuit when it is embedded in another circuit. Is not used for
DIL packages.
Description
A short description of this element and its usage.
Oscillation detection
Number of gate propagation times at which a oscillation is detected if the circuit has
not stabilized by then.
Modification locked
The circuit is locked. It is possible to configure diodes and FGF-FETs.
Shape
The shape to be used for the representation of the circuit in an embedding circuit. In
the "Simple" mode, the inputs are displayed on the left and the outputs on the right
side of a simple rectangle. With "Layout", the position of the inputs and outputs and
their orientation in the circuit determines the position of the pins. Here it is possible
to have pins at the top or the bottom. When selecting "DIL-Chip", a DIL housing is
used to display the circuit. The pin numbers of the inputs and outputs determine the
position of the pins in this case.
Custom Shape
Import of a SVG file
Height
Height of symbol if this circuit is used as an component in an other circuit.

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Number of DIL pins

Number of pins. A zero means that the number of pins is determined automatically.
Content of ROMs
Content of all used ROMs
Show measurement values at simulation start
When the simulation is started, a table with the measured values is shown.
Show measurement graph at simulation start
When the simulation is started, a graph with the measured values is shown.
Show measurement graph in single gate step mode at simulation start
When the simulation is started, a graph with the measured values in the gate step
mode is shown. All gate changes are included in the graph.
Max number of steps to show
The maximal number of values stored. If the maximum number is reached, the oldest
values are discarded.
Preload program memory at startup.
When simulating a processor that uses a RAM device as the program memory, it is
difficult to start this processor because the RAM contents are always initialized with
zeros at the start of the simulation. This setting allows loading data into the program
memory at startup. The program memory in the simulation must be marked as such.
Program file
File which should be loaded into the program memory at the start of the simulation.
Use big endian at import.
Use big endian byte order at import.
Skip in Verilog/VHDL export
Skips generating the internals of the circuit in Verilog/VHDL export. The references to
the circuit are kept, making it possible to override the implementation.
Circuit is generic
Allows to create a generic circuit.

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C Command Line Interface

java -cp Digital.jar CLI
test -circ [String] [-tests [String]] [-allowMissingInputs] [-verbose]:
The first file name specifies the circuit to be tested. If a second file name is specified,
the test cases are executed from this file. If no second file name is specified, the tests
are executed from the first file.
Options:
-circ [String(def: )]
Name of the file to be tested.
[-tests [String(def: )]]
Name of a file with test cases.
[-allowMissingInputs(def: false)]
Allows the lack of inputs in the circuit which are defined in the test case. This can
be useful if there are several possible solutions which may depend on different
inputs.
[-verbose(def: false)]
If set, the value table is output in case of an error.
svg -dig [String] [-svg [String]] [-ieee] [-LaTeX] [-pinsInMathMode] [-hideTest] [-
noShapeFilling] [-smallIO] [-noPinMarker] [-thinnerLines] [-highContrast] [-monochrome]:
Can be used to create an SVG file from a circuit.
Options:
-dig [String(def: )]
The file name of the circuit.
[-svg [String(def: )]]
The name of the SVG file to be written.
[-ieee(def: false)]
Use the IEEE symbols.
[-LaTeX(def: false)]
Text is inserted in LaTeX notation. Inkscape is required for further processing.
[-pinsInMathMode(def: false)]
For pin labels, use math mode even if no indexes are contained.
[-hideTest(def: false)]
Hide Test Cases
[-noShapeFilling(def: false)]
Polygons are not filled.
[-smallIO(def: false)]

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Inputs and outputs are represented as small circles.

[-noPinMarker(def: false)]
The blue and red pin markers on the symbols are omitted.
[-thinnerLines(def: false)]
If set, the lines are drawn slightly thinner.
[-highContrast(def: false)]
The wires and the text of the pins are displayed in black.
[-monochrome(def: false)]
Only gray colors are used.
stats -dig [String] [-csv [String]]:
Creates a CSV file which contains the circuit statistics. All components used are listed
in the CSV file.
Options:
-dig [String(def: )]
File name of the circuit.
[-csv [String(def: )]]
Name of the CSV file to be created. If this option is missing, the table is written to
stdout.

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D Components
1. Logic

1.1. And

Binary AND gate. Returns high only if all inputs are also set high. It is also possible to use
buses with several bits as inputs and output. In this case, a bitwise AND is executed. This
means that the lowest bits of all inputs are connected with AND and is output as the lowest
bit at the output. The same happens with bit 1, bit 2 and so on. Exportable to VHDL/Verilog.
Inputs
In_1
The 1. input value for the logic operation.
In_2
The 2. input value for the logic operation.
Outputs
out
Returns the result of the logic operation.
Attributes
Data Bits
Number of data bits used.
Number of Inputs
The Number of Inputs used. Every input needs to be connected.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Wide Shape
Uses a wider shape to visualize the gate.

1.2. NAnd

A combination of AND and NOT. Returns 0 only if all inputs are set to 1. If one of the inputs
is set to 0 the output is set to 1. It is also possible to use buses with several bits per input. In
this case, the operation is applied to each bit of the inputs. Exportable to VHDL/Verilog.

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Inputs
In_1
The 1. input value for the logic operation.
In_2
The 2. input value for the logic operation.
Outputs
out
Returns the result of the logic operation.
Attributes
Data Bits
Number of data bits used.
Number of Inputs
The Number of Inputs used. Every input needs to be connected.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Wide Shape
Uses a wider shape to visualize the gate.

1.3. Or

Binary OR gate. Returns a 1 if one of the inputs is set to 1. If all inputs are set to 0 the output
is also set to 0. It is also possible to use buses with several bits as inputs and output. In this
case, a bitwise OR is executed. This means that the lowest bits of all inputs are connected
with OR and is output as the lowest bit at the output. The same happens with bit 1, bit 2 and
so on. Exportable to VHDL/Verilog.
Inputs
In_1
The 1. input value for the logic operation.
In_2
The 2. input value for the logic operation.
Outputs
out
Returns the result of the logic operation.
Attributes
Data Bits
Number of data bits used.
Number of Inputs
The Number of Inputs used. Every input needs to be connected.

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Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Wide Shape
Uses a wider shape to visualize the gate.

1.4. NOr

A combination of OR and NOT. Returns a 0 if one of the inputs is set to 1. If all inputs are set
to 0 the output is also set to 1. It is also possible to use buses with several bits per input. In
this case, the operation is applied to each bit of the inputs. Exportable to VHDL/Verilog.
Inputs
In_1
The 1. input value for the logic operation.
In_2
The 2. input value for the logic operation.
Outputs
out
Returns the result of the logic operation.
Attributes
Data Bits
Number of data bits used.
Number of Inputs
The Number of Inputs used. Every input needs to be connected.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Wide Shape
Uses a wider shape to visualize the gate.

1.5. XOr

If two inputs are used, the output is 0 if both input bits are equal. Otherwise the output in set
to 1. If more than two inputs are used, it behaves like cascaded XOR gates ( A XOR B XOR
C = (A XOR B) XOR C ). It is also possible to use buses with several bits per input. In this
case, the operation is applied to each bit of the inputs. Exportable to VHDL/Verilog.

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Inputs
In_1
The 1. input value for the logic operation.
In_2
The 2. input value for the logic operation.
Outputs
out
Returns the result of the logic operation.
Attributes
Data Bits
Number of data bits used.
Number of Inputs
The Number of Inputs used. Every input needs to be connected.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Wide Shape
Uses a wider shape to visualize the gate.

1.6. XNOr

A combination of XOR and NOT. The inputs are combined with the XOR operation. The
result of this operation is then inverted. It is also possible to use buses with several bits per
input. In this case, the operation is applied to each bit of the inputs. Exportable to VHDL/
Verilog.
Inputs
In_1
The 1. input value for the logic operation.
In_2
The 2. input value for the logic operation.
Outputs
out
Returns the result of the logic operation.
Attributes
Data Bits
Number of data bits used.
Number of Inputs
The Number of Inputs used. Every input needs to be connected.
Inverted inputs
You can select the inputs that are to be inverted.

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Rotation
The orientation of the Element in the circuit.
Wide Shape
Uses a wider shape to visualize the gate.

1.7. Not

Inverts the input value. A 1 becomes a 0 and a 0 becomes 1. It is also possible to use a bus
with several bits per input. In this case, the operation is applied to each bit of the inputs.
Exportable to VHDL/Verilog.
Inputs
in
The input of the NOT gate.
Outputs
out
The inverted input value.
Attributes
Data Bits
Number of data bits used.
Rotation
The orientation of the Element in the circuit.
Wide Shape
Uses a wider shape to visualize the gate.

0
out
1
LUT

1.8. Lookup Table

Gets the output value from a stored table. So this gate can emulate every combinatorial gate.
Exportable to VHDL/Verilog.
Inputs
0
Input 0. This input in combination with all other inputs defines the address of the
stored value to be returned.
1
Input 1. This input in combination with all other inputs defines the address of the
stored value to be returned.
Outputs
out
Returns the stored value at the address set via the inputs.

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Attributes
Data Bits
Number of data bits used.
Number of Inputs
The Number of Inputs used. Every input needs to be connected.
Label
The name of this element.
Data
The values stored in this element.
Rotation
The orientation of the Element in the circuit.

2. IO

2.1. Output

Can be used to display an output signal in a circuit. This element is also used to connect a
circuit to an embedding circuit. In this case the connection is bidirectional. Is also used to
assign a pin number, if the code for a CPLD or FPGA is generated. Exportable to VHDL/
Verilog.
Inputs
in
This value is used for the output connection.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Description
A short description of this element and its usage.
Rotation
The orientation of the Element in the circuit.
Number Format
The format used to show the numbers.
fixed point digits
Number of fractional binary digits
Pin number
Number of this pin. Used for the representation of a circuit as a DIL package and the
pin assignment when programming a CPLD. If there are several bits, all pin numbers
can be specified as a comma-separated list.
Show in Measurement Graph
Shows the value in the measurement graph.
Small Shape
If selected, a smaller shape will be used.

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2.2. LED

A LED can be used to visualize an output value. Accepts a single bit. Lights up if the input is
set to 1.
Inputs
in
LED Input. LED lights up if the input is set to 1.
Attributes
Label
The name of this element.
Color
The Color of the element.
Rotation
The orientation of the Element in the circuit.
Size
The size of the shape in the circuit.

2.3. Input

Can be used to interactively manipulate an input signal in a circuit with the mouse. This
element is also used to connect a circuit to an embedding circuit. In this case the connection
is bidirectional. Is also used to assign an pin number, if code for a CPLD or FPGA is
generated. Exportable to VHDL/Verilog.
Outputs
out
Gives the value which is connected to this input.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Description
A short description of this element and its usage.
Rotation
The orientation of the Element in the circuit.
Default
This value is set if the circuit is started. A "Z" means high-z state.
Is three-state input
If set the input is allowed to be in high-z state. At the input component this is also
allowed if high-z ("Z") is set as the default value.

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No zero output.
Avoids zero output. This is especially helpful when setting up relay circuits. Can only
be activated if a high-z output is allowed.
Number Format
The format used to show the numbers.
fixed point digits
Number of fractional binary digits
Pin number
Number of this pin. Used for the representation of a circuit as a DIL package and the
pin assignment when programming a CPLD. If there are several bits, all pin numbers
can be specified as a comma-separated list.
Show in Measurement Graph
Shows the value in the measurement graph.
Small Shape
If selected, a smaller shape will be used.

2.4. Clock Input

A clock signal. It's possible to control it by a real-time clock. Depending on the complexity
of the circuit, the clock frequency achieved may be less than the selected value. If the
frequency is greater than 50Hz, the graphic representation of the circuit will no longer be
updated at every clock cycle so that the wire colors will no longer be updated. If the real-time
clock is not activated, the clock can be controlled by mouse clicks. Is also used to assign an
pin number, if code for a CPLD or FPGA is generated. Exportable to VHDL/Verilog.
Outputs
C
Switches between 0 and 1 with the selected clock frequency.
Attributes
Label
The name of this element.
Start real time clock
If enabled the runtime clock is started when the circuit is started
Frequency/Hz
The real time frequency used for the real time clock
Rotation
The orientation of the Element in the circuit.
Pin number
Number of this pin. Used for the representation of a circuit as a DIL package and the
pin assignment when programming a CPLD. If there are several bits, all pin numbers
can be specified as a comma-separated list.
Small Shape
If selected, a smaller shape will be used.

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2.5. Button

A simple push button which goes back to its original state when it is released.
Outputs
out
The output signal of the button.
Attributes
Label
The name of this element.
Active Low
If selected the output is low if the component is active.
Map to keyboard
Button is mapped to the keyboard. To use the cursor keys use UP, DOWN, LEFT or
RIGHT as label.
Rotation
The orientation of the Element in the circuit.
Show in Measurement Graph
Shows the value in the measurement graph.

2.6. DIP Switch

Simple DIP switch that can output either high or low.

Outputs
out
The output value of the switch.
Attributes
Label
The name of this element.
Description
A short description of this element and its usage.
Rotation
The orientation of the Element in the circuit.
Output is High
The default output value of the DIP switch when the simulation starts.

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2.7. Probe

A measurement value which can be shown in the data graph or measurement table. This
component can be used to easily observe values from embedded circuits. Does not affect
the simulation.
Inputs
in
The measurement value.
Attributes
Label
The name of this element.
Display Mode
Defines whether the value or a counter is to be displayed.
Rotation
The orientation of the Element in the circuit.
Number Format
The format used to show the numbers.
fixed point digits
Number of fractional binary digits
Show in Measurement Graph
Shows the value in the measurement graph.

A
B
C

2.8. Data Graph

Shows a data plot inside of the circuit panel. You can plot complete clock cycles or single
gate changes. Does not affect the simulation.
Attributes
Show single gate steps
Shows all single step steps in the graphic.
Max number of steps to show
The maximal number of values stored. If the maximum number is reached, the oldest
values are discarded.
Snap To Grid
If set, the component is aligned with the grid.

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2.9. Triggered Data Graph

Shows a graph of measured values, whereby measured values are only stored if the input
signal changes. Storing takes place when the circuit has stabilized. The trigger does not start
the measurement like in a real scope, but each trigger event stores a single measurement
value for each of the shown signals. As direct input there is only the trigger. The inputs
and outputs of the circuit, flip-flops and registers and the probe component can be used as
signals. This can be activated in the respective components.
Inputs
T
A change at this input causes measured values to be stored.
Attributes
Label
The name of this element.
Trigger
Trigger condition for data recording.
Max number of steps to show
The maximal number of values stored. If the maximum number is reached, the oldest
values are discarded.

3. IO - Displays

3.1. RGB-LED

An RGB LED whose color can be controlled via three inputs. At each of the three inputs, a
color channel is connected.
Inputs
R
The red color channel.
G
The green color channel.
B
The blue color channel.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.

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Rotation
The orientation of the Element in the circuit.
Size
The size of the shape in the circuit.

3.2. LED with two connections.

LED with connections for the cathode and the anode. The LED lights up if the anode is
connected to high and the cathode is connected to low. This LED cannot be used as a
pull-down resistor. It acts solely as a display element. The shown resistor is only meant to
symbolize the required series resistor to limit the current.
Inputs
A
The anode connection of the LED.
C
The cathode connection of the LED.
Attributes
Label
The name of this element.
Color
The Color of the element.
Rotation
The orientation of the Element in the circuit.

3.3. Button with LED

A simple push button which goes back to its original state when it is released. The push
button has an LED which can be switched via an input signal.
Inputs
in
Input for controlling the LED.
Outputs
out
The output signal of the button.
Attributes
Label
The name of this element.

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Active Low
If selected the output is low if the component is active.
Map to keyboard
Button is mapped to the keyboard. To use the cursor keys use UP, DOWN, LEFT or
RIGHT as label.
Color
The Color of the element.
Rotation
The orientation of the Element in the circuit.

3.4. Seven-Segment Display

Seven Segment Display, every segment has its own control input.
Inputs
a
This input controls the upper, horizontal line.
b
This input controls the upper, right, vertical line.
c
This input controls the lower, right, vertical line.
d
This input controls the lower horizontal line.
e
This input controls the lower, left, vertical line.
f
This input controls the upper, left, vertical line.
g
This input controls the middle, horizontal line.
dp
This input controls the decimal point.
Attributes
Color
The Color of the element.
Common Connection
If selected, a common cathode or anode input is also simulated.
Common
Kind of common connection.
Persistence Of Vision
Specifies the duration of the afterglow. The larger the value, the longer the afterglow
duration.

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3.5. Seven-Segment Hex Display

Seven Segment Display with a 4 bit hex input

Inputs
d
The value at this input is visualized at the display.
dp
This input controls the decimal point.
Attributes
Color
The Color of the element.
Size
The size of the shape in the circuit.

3.6. 16-Segment Display

The LED input has 16 bits which control the segments. The second input controls the
decimal point.
Inputs
led
16-bit bus for driving the LEDs.
dp
This input controls the decimal point.
Attributes
Color
The Color of the element.
Size
The size of the shape in the circuit.

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3.7. Light Bulb

Light bulb with two connections. If a current flows, the bulb lights up! The direction of the
current does not matter. The lamp lights when the inputs have different values. The bulb
behaves similar to an XOr gate.
Inputs
A
Connection
B
Connection
Attributes
Label
The name of this element.
Color
The Color of the element.
Rotation
The orientation of the Element in the circuit.

r-data
c-addr
LED-Matrix

3.8. LED-Matrix

A matrix of LEDs. The LEDs are shown in a separate window. The LEDs of a column of the
display are controlled by a data word. At another input, the current column is selected. So a
multiplexed display is realized. The LEDs are able to light up indefinitely in the simulation to
prevent the display from flickering.
Inputs
r-data
The row state of the LEDs of a column. Each bit in this data word represents the state
of a row of the current column.
c-addr
The number of the current column whose state is currently visible at the other input.
Attributes
Label
The name of this element.
Rows
Specifies the number of rows by specifying the number of bits of the row word.
Address bits of columns
Addresses the individual columns. Three bits means eight columns.

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Color
The Color of the element.
Avoid Flicker
It is not possible to increase the frequency so much that the flickering disappears. In
order to suppress the flickering nevertheless, a "afterglow" can be switched on for the
LEDs with this option. If enabled, the LEDs remain on, even if one of the pins changes
to high-z. This simulates a frequency above the critical flicker fusion frequency.
Rotation
The orientation of the Element in the circuit.

4. IO - Mechanical

4.1. Rotary Encoder

Rotary knob with rotary encoder. Used to detect rotational movements.

Outputs
A
encoder signal A
B
encoder signal B
Attributes
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.

4.2. Stepper Motor, unipolar

Unipolar stepper motor with two limit position switches. Full step drive, half step drive and
wave drive are supported.

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Inputs
P0
Phase 0
P1
Phase 1
P2
Phase 2
P3
Phase 3
com
Common center coil connection
Outputs
S0
Limit position switch 0, becomes 1 when the motor angle is 0°.
S1
Limit position switch 1, becomes 1 when the motor angle is 180°.
Attributes
Label
The name of this element.
Inverted output
If selected the output is inverted.
Rotation
The orientation of the Element in the circuit.

4.3. Stepper Motor, bipolar

Bipolar stepper motor with two limit position switches. Full step drive, half step drive and
wave drive are supported.
Inputs
A+
Coil A, positive
A-
Coil A, negative
B+
Coil B, positive
B-
Coil B, negative

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Outputs
S0
Limit position switch 0, becomes 1 when the motor angle is 0°.
S1
Limit position switch 1, becomes 1 when the motor angle is 180°.
Attributes
Label
The name of this element.
Inverted output
If selected the output is inverted.
Rotation
The orientation of the Element in the circuit.

5. IO - Peripherals

C D
en av
Keyboard

5.1. Keyboard

A keyboard that can be used to enter text. This component buffers the input, which can then
be read out. A separate window is opened for the text input.
Inputs
C
Clock. A rising edge removes the oldest character from the buffer.
en
If high, the output D is active and one character is output. It also enables the clock
input.
Outputs
D
The last typed character, or zero if no character is available. Output is the 16 bit Java
char value.
av
This output indicates that characters are available. It can be used to trigger an
interrupt.
Attributes
Label
The name of this element.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.

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D
C
en
Terminal

5.2. Terminal

You can write ASCII characters to this terminal. The terminal opens its own window to
visualize the output.
Inputs
D
The data to write to the terminal
C
Clock. A rising edge writes the value at the input to the terminal window.
en
A high at this input enables the clock input.
Attributes
Characters per line
The number of characters shown in a single line.
Lines
The number of lines to show.
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.

in out
C av
wr
rd
Telnet

5.3. Telnet

Allows a Telnet connection to the circuit. It is possible to receive and send characters via
Telnet.
Inputs
in
The data to be sent.
C
Clock input
wr
If set, the input data byte is sent.
rd
If set, a received byte is output.

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Outputs
out
Data output
av
Outputs a one if data is present.
Attributes
Label
The name of this element.
Telnet mode
If set, the Telnet control commands are evaluated. In addition, the server sends the
SGA and ECHO commands. If this option is disabled, the server is a simple TCP
server.
Port
The port to be opened by the server.
Rotation
The orientation of the Element in the circuit.

R
G
B
H
V
C
VGA

5.4. VGA Monitor

Analyzes the incoming video signals and displays the corresponding graphic. Since the
simulation cannot run in real time, the pixel clock is required in addition to the video signals.
Inputs
R
The red color component
G
The green color component
B
The blue color component
H
The horizontal synchronization signal
V
The vertical synchronization signal
C
The pixel clock
Attributes
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.

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 Digital

N
V
OnOff
en
C
MIDI

5.5. MIDI

Uses the MIDI system to play notes.

Inputs
N
Note
V
Volume
OnOff
If set, this translates to pressing a keyboard key (key down event), if not set, this
translates to releasing the key (key up event).
en
Enables the component
C
Clock
Attributes
Label
The name of this element.
MIDI channel
Selects the MIDI channel to use.
MIDI instrument
The MIDI instrument to use.
Allow program change
Adds a new input PC. If this input is set to high, the value at input N is used to change
the program (instrument).
Rotation
The orientation of the Element in the circuit.

6. Wires

6.1. Ground

A connection to ground. Output is always zero. Exportable to VHDL/Verilog.

Outputs
out
Output always returns 0.

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Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.

6.2. Supply voltage

A connection to the supply voltage. Output is always one. Exportable to VHDL/Verilog.

Outputs
out
This output always returns 1.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.

6.3. Constant value

A component which returns a given value as a simple constant value. The value can be set
in the attribute dialog. Exportable to VHDL/Verilog.
Outputs
out
Returns the given value as a constant.
Attributes
Data Bits
Number of data bits used.
Value
The value of the constant.
Rotation
The orientation of the Element in the circuit.
Number Format
The format used to show the numbers.
fixed point digits
Number of fractional binary digits

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6.4. Tunnel

Connects components without a wire. All tunnel elements, which have the same net name,
are connected together. Works only locally, so it is not possible to connect different circuits.
Unnamed tunnels are ignored silently. Exportable to VHDL/Verilog.
Inputs
in
The connection to the tunnel.
Attributes
Net name
All nets with identical name are connected together.
Rotation
The orientation of the Element in the circuit.

0-3 0-7
4-7

6.5. Splitter/Merger

Splits or creates a wire bundle or a data bus with more than one bit. With a bus it is e.g.
possible to generate 16-bit connections without having to route 16 individual wires. All 16
connections can be merged into one wire. The splitter has a direction, meaning it can only
transmit signals in one direction. Exportable to VHDL/Verilog.
Inputs
0-3
The input bits 0-3.
4-7
The input bits 4-7.
Outputs
0-7
The output bits 0-7.
Attributes
Input Splitting
If e.g. four bits, two bits and two further bits are to be used as inputs, this can be
configured with "4,2,2". The number indicates the number of bits. For convenience,
the asterisk can be used: 16 bits can be configured with "[Bits]*[Number]" as "1*16". It
is also possible to specify the bits to be used directly and in any order. For example,
"4-7,0-3" configures bits 4-7 and 0-3. This notation allows any bit arrangement. The
input bits must be specified completely and unambiguously.

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Output splitting
If e.g. four bits, two bits and two further bits are to be used as outputs, this can be
configured with "4,2,2". The number indicates the number of bits. For convenience,
the asterisk can be used: 16 bits can be configured with "[Bits]*[Number]" as "1*16". It
is also possible to specify the bits to be used directly and in any order. For example,
"4-7,0-3" configures bits 4-7 and 0-3. This notation allows any bit arrangement. Output
bits can also be output several times: "0-7,1-6,4-7".
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.
Spreading
Configures the spread of the inputs and outputs in the circuit.

6.6. Driver

A driver can be used to connect a signal value to another wire. The driver is controlled by the
sel input. If the sel input is low, the output is in high z state. If the sel input is high, the output
is set to the input value. Exportable to VHDL/Verilog.
Inputs
in
The input value of the driver.
sel
Pin to control the driver. If its value is 1 the input is set to the output. If the value is 0,
the output is in high z state.
Outputs
out
If the sel input is 1 the input is given to this output. If the sel input is 0, this output is in
high z state.
Attributes
Data Bits
Number of data bits used.
Flip selector position
This option allows you to move te selector pin to the opposite side of the plexer.
Rotation
The orientation of the Element in the circuit.

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6.7. Driver, inverted select

A driver can be used to connect a data word to another line. The driver is controlled by the
sel input. If the sel input is high, the output is in high z state. If the sel input is low, the output
is set to the input value. Exportable to VHDL/Verilog.
Inputs
in
The input value of the driver.
sel
Pin to control the driver. If its value is 0 the input is given to the output. If the value is
1, the output is in high z state.
Outputs
out
If the sel input is 1 the input is given to this output. If the sel input is 0, this output is in
high z state.
Attributes
Data Bits
Number of data bits used.
Flip selector position
This option allows you to move te selector pin to the opposite side of the plexer.
Rotation
The orientation of the Element in the circuit.

6.8. Delay

Delays the signal by one propagation delay time. Delays a signal for an adjustable number of
gate delays. All other components in Digital have a gate delay of one propagation delay time.
This component can be used to realize any necessary propagation delay.
Inputs
in
Input of the signal to be delayed.
Outputs
out
The input signal delayed by one gate delay time.
Attributes
Data Bits
Number of data bits used.

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Duration
Delay time in units of the common gate propagation delay.
Rotation
The orientation of the Element in the circuit.

6.9. Pull-Up Resistor

If a net is in a HighZ state, this resistor pulls the net to high. In any other case this
component has no effect.
Outputs
out
A "weak high".
Attributes
Data Bits
Number of data bits used.
Rotation
The orientation of the Element in the circuit.

6.10. Pull-Down Resistor

If the net is in a HighZ state, this resistor pulls the net to ground. In any other case this
component has no effect.
Outputs
out
A "weak low".
Attributes
Data Bits
Number of data bits used.
Rotation
The orientation of the Element in the circuit.

6.11. Not Connected

This component can be used to set a wire to High-Z. If an input of a logical gate is set to
high-Z, the read value is undefined. Note that in reality in many cases excessive current
consumption and even damage can occur if a digital input is not set to high or low but
remains unconnected.

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Outputs
out
This output always outputs High-Z.
Attributes
Data Bits
Number of data bits used.

7. Plexers

7.1. Multiplexer

A component which uses the value of the sel pin to decide which input value is set to the
output. Exportable to VHDL/Verilog.
Inputs
sel
This input is used to select the data input which is output.
in_0
The 0. data input of the multiplexer.
in_1
The 1. data input of the multiplexer.
Outputs
out
The value of the selected input.
Attributes
Data Bits
Number of data bits used.
Number of Selector Bits
Number of bits used for the selector input.
Flip selector position
This option allows you to move te selector pin to the opposite side of the plexer.
Rotation
The orientation of the Element in the circuit.

7.2. Demultiplexer

A component that can output the input value to one of the outputs. The other outputs are set
to the default value. Exportable to VHDL/Verilog.

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Inputs
sel
This pin selects the output to use.
in
The value of this input is given to the selected data output.
Outputs
out_0
Data output 0.
out_1
Data output 1.
Attributes
Data Bits
Number of data bits used.
Number of Selector Bits
Number of bits used for the selector input.
Flip selector position
This option allows you to move te selector pin to the opposite side of the plexer.
Rotation
The orientation of the Element in the circuit.
Default
This value is set if the circuit is started. At the demultiplexer, this value is set for the
non-selected outputs.

7.3. Decoder

One selectable output pin is 1, all other outputs are set to 0. Exportable to VHDL/Verilog.
Inputs
sel
This input selects the enabled output. The selected output is set to 1. All other outputs
are set to 0.
Outputs
out_0
Output 0. This output is 1 if selected by the sel input.
out_1
Output 1. This output is 1 if selected by the sel input.
Attributes
Number of Selector Bits
Number of bits used for the selector input.
Flip selector position
This option allows you to move te selector pin to the opposite side of the plexer.

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Rotation
The orientation of the Element in the circuit.

7.4. Bit Selector

Selects a single bit from a data bus. Exportable to VHDL/Verilog.

Inputs
in
The input bus
sel
This input selects the bit
Outputs
out
The selected bit.
Attributes
Number of Selector Bits
Number of bits used for the selector input.
Flip selector position
This option allows you to move te selector pin to the opposite side of the plexer.
Rotation
The orientation of the Element in the circuit.

in0 num
in1 any
Priority

7.5. Priority Encoder

If one of the inputs is set, its number is output. If several inputs are set at the same time, the
highest number is output. Exportable to VHDL/Verilog.
Inputs
in0
The 0. input of the priority encoder.
in1
The 1. input of the priority encoder.
Outputs
num
Number of the set input.
any
If this output is set, at least one of the inputs is set.
Attributes

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Label
The name of this element.
Number of Selector Bits
Number of bits used for the selector input.
Rotation
The orientation of the Element in the circuit.

8. Flip-Flops

S Q
R Q
RS

8.1. RS-Flip-flop

A component to store a single bit. Provides the functions "set" and "reset" to set or reset the
stored bit. If both inputs are switched to one, both outputs also output a one. If both inputs
switch back to zero at the same time, the final state is random.
Inputs
S
The set input.
R
The reset input.
Outputs
Q
Returns the stored value.
¬Q
Returns the inverted stored value.
Attributes
Label
The name of this element.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.
Default
This value is set if the circuit is started. At the demultiplexer, this value is set for the
non-selected outputs.
Use as measurement value
If set the value is a measurement value and appears in the graph and data table. In
addition, a label must be specified that can serve as identification of the value.

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S Q
C Q
R
RS

8.2. RS-Flip-flop, clocked

A component to store a single bit. Provides the functions "set" and "reset" to set or reset
the stored bit. If both inputs (S, R) are set at the rising edge of the clock, the final state is
random.
Inputs
S
The set input.
C
The clock input. A rising edge initiates a state transition.
R
The reset input.
Outputs
Q
Returns the stored value.
¬Q
Returns the inverted stored value.
Attributes
Label
The name of this element.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.
Default
This value is set if the circuit is started. At the demultiplexer, this value is set for the
non-selected outputs.
Use as measurement value
If set the value is a measurement value and appears in the graph and data table. In
addition, a label must be specified that can serve as identification of the value.

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J Q
C Q
K
JK

8.3. JK-Flip-flop

Has the possibility to store (J=K=0), set (J=1, K=0), reset (J=0, K=1) or toggle (J=K=1)
the stored value. A change of state takes place only at a rising edge at the clock input C.
Exportable to VHDL/Verilog.
Inputs
J
The set input of the flip-flop.
C
The clock input. A rising edge initiates a state change.
K
The reset input of the flip-flop.
Outputs
Q
Returns the stored value.
¬Q
Returns the inverted stored value.
Attributes
Label
The name of this element.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.
Default
This value is set if the circuit is started. At the demultiplexer, this value is set for the
non-selected outputs.
Use as measurement value
If set the value is a measurement value and appears in the graph and data table. In
addition, a label must be specified that can serve as identification of the value.

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D Q
C Q
D

8.4. D-Flip-flop

A component used to store a value. The value on pin D is stored on a rising edge of the clock
pin C. The bit width can be selected, which allows to store multiple bits. Exportable to VHDL/
Verilog.
Inputs
D
Input of the bit to be stored.
C
Clock pin to store a value. The value on input D is stored on a rising edge of this pin.
Outputs
Q
Returns the stored value.
¬Q
Returns the inverted stored value.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.
Default
This value is set if the circuit is started. At the demultiplexer, this value is set for the
non-selected outputs.
Use as measurement value
If set the value is a measurement value and appears in the graph and data table. In
addition, a label must be specified that can serve as identification of the value.

T Q
C Q
T

8.5. T-Flip-Flop

Stores a single bit. Toggles the state on a rising edge at input C.

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Inputs
T
Enables the toggle function.
C
Clock input. A rising edge toggles the output, if input T is set to 1.
Outputs
Q
Returns the stored value.
¬Q
Returns the inverted stored value.
Attributes
Label
The name of this element.
Enable Input
If set an enable input (T) is available.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.
Default
This value is set if the circuit is started. At the demultiplexer, this value is set for the
non-selected outputs.
Use as measurement value
If set the value is a measurement value and appears in the graph and data table. In
addition, a label must be specified that can serve as identification of the value.

Set Q
J Q
C
K
Clr
JK-AS

8.6. JK-Flip-flop, asynchronous

Has the possibility to store (J=K=0), set (J=1, K=0), reset (J=0, K=1) or toggle (J=K=1) the
stored value. A change of state takes place only at a rising edge at the clock input C. There
are two additional inputs which set or reset the state immediately without a clock signal.
Exportable to VHDL/Verilog.

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Inputs
Set
asynchronous set. A high value at this input sets the flip-flop.
J
The set input of the flip-flop.
C
The Clock input. A rising edge initiates a state change.
K
The reset input of the flip-flop.
Clr
asynchronous clear. A high value at this input clears the flip-flop.
Outputs
Q
Returns the stored value.
¬Q
Returns the inverted stored value.
Attributes
Label
The name of this element.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.
Default
This value is set if the circuit is started. At the demultiplexer, this value is set for the
non-selected outputs.
Use as measurement value
If set the value is a measurement value and appears in the graph and data table. In
addition, a label must be specified that can serve as identification of the value.

Set Q
D Q
C
Clr
D-AS

8.7. D-Flip-flop, asynchronous

A component used to store a value. The value on pin D is stored on a rising edge of the clock
pin C. There are two additional inputs which set or reset the state immediately without a
clock signal. The bit width can be selected, which allows to store multiple bits. Exportable to
VHDL/Verilog.

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Inputs
Set
asynchronous set. If set to one, all stored bits are set to one.
D
Input of the bit to be stored.
C
Control pin to store a bit. The bit on input D is stored on a rising edge of this pin.
Clr
asynchronous clear. If set to one, all stored bits are set to zero.
Outputs
Q
Returns the stored value.
¬Q
Returns the inverted stored value.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.
Default
This value is set if the circuit is started. At the demultiplexer, this value is set for the
non-selected outputs.
Use as measurement value
If set the value is a measurement value and appears in the graph and data table. In
addition, a label must be specified that can serve as identification of the value.

C Q
R Q
Mono

8.8. Monoflop

The monoflop is set at a rising edge at the clock input. After a configurable delay time, the
monoflop will be cleared automatically. The monoflop is retriggerable. It can only be used if
there is exactly one clock component present in the circuit. This clock component is used as
time base to measure the time delay.

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Inputs
C
The Clock input. A rising edge sets the monoflop.
R
Reset Input. A high value clears the monoflop.
Outputs
Q
output
¬Q
inverted output
Attributes
Label
The name of this element.
Pulse Width
The pulse width is measured in clock cycles.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.
Default
This value is set if the circuit is started. At the demultiplexer, this value is set for the
non-selected outputs.
Use as measurement value
If set the value is a measurement value and appears in the graph and data table. In
addition, a label must be specified that can serve as identification of the value.

9. Memory - RAM

A
Din
str D
C
ld
RAM

9.1. RAM, separated Ports

A RAM module with separate inputs for storing and output for reading the stored data.
Exportable to VHDL/Verilog.

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Inputs
A
The address to read from or write to.
Din
The data to be stored in the RAM.
str
If this input is high and when the clock becomes high, the data is stored.
C
Clock input
ld
If this input is high the output is activated and the data is visible at the output.
Outputs
D
The data output pin
Attributes
Data Bits
Number of data bits used.
Address Bits
Number of address bits used.
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.
Number Format
The format used to show the numbers.
fixed point digits
Number of fractional binary digits
Program Memory
Makes this ROM to program memory. So it can be accessed by an external IDE.

A
Din
D
str
C
RAM

9.2. Block-RAM, separated ports

A RAM module with separate inputs for storing and output for reading the stored data. This
RAM only updates its output on a rising edge of the clock input. This allows the usage of
Block RAM on an FPGA. Exportable to VHDL/Verilog.

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Inputs
A
The address to read from or write to.
Din
The data to be stored in the RAM.
str
If this input is high and when the clock becomes high, the data is stored.
C
Clock input
Outputs
D
The data output pin
Attributes
Data Bits
Number of data bits used.
Address Bits
Number of address bits used.
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.
Program Memory
Makes this ROM to program memory. So it can be accessed by an external IDE.

A
str
D
C
ld
RAM

9.3. RAM, bidirectional Port

A RAM module with a bidirectional pin for reading and writing the data.
Inputs
A
The address to read and write.
str
If this input is high when the clock becomes high, the data is stored.
C
Clock
ld
If this input is high the output is activated and the data is visible at the output.
Outputs
D
The bidirectional data connection.

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Attributes
Data Bits
Number of data bits used.
Address Bits
Number of address bits used.
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.
Number Format
The format used to show the numbers.
fixed point digits
Number of fractional binary digits
Program Memory
Makes this ROM to program memory. So it can be accessed by an external IDE.

A
CS
D
WE
OE
RAM

9.4. RAM, Chip Select

A RAM module with a bidirectional connection for reading and writing the data. If the CS
input is low, the component is disabled. This allows to build a larger RAM from some smaller
RAMs and a address decoder. The write cycle works as follows: By setting CS to high, the
component is selected. A rising edge at WE latches the address, and the following falling
edge at WE stores the data.
Inputs
A
The address to read and write.
CS
If this input is high, this RAM is enabled. Otherwise the output is always in high Z
state.
WE
If set to high the data is written to the RAM.
OE
If this input is high, the stored value is output.
Outputs
D
The bidirectional data connection.
Attributes
Data Bits
Number of data bits used.

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Address Bits
Number of address bits used.
Label
The name of this element.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Program Memory
Makes this ROM to program memory. So it can be accessed by an external IDE.

Din Da
we Db
Rw
C
Ra
Rb
Register

9.5. Register File

Memory with one port that allows to write and two ports that allow to read from the memory
simultaneously. Can be used to implement processor registers. Two registers can be read
simultaneously and a third can be written. Exportable to VHDL/Verilog.
Inputs
Din
The data to be stored in the register Rw.
we
If this input is high and when the clock becomes high, the data is stored.
Rw
The register into which the data is written.
C
Clock
Ra
The register which is visible at port a.
Rb
The register which is visible at port b.
Outputs
Da
Output Port a
Db
Output Port b
Attributes
Data Bits
Number of data bits used.
Address Bits
Number of address bits used.

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Label
The name of this element.
Rotation
The orientation of the Element in the circuit.

str 1D
C 2D
ld
1A
1Din
2A
RAM

9.6. RAM, Dual Port

RAM with one port that allows to write to and read from the RAM, and a second read
only port. This second port can be used to give some graphic logic access to the memory
contents. In this way, a processor can write to the RAM, and a graphics logic can
simultaneously read from the RAM. Exportable to VHDL/Verilog.
Inputs
str
If this input is high and when the clock becomes high, the data is stored.
C
Clock
ld
If this input is high the output is activated and the data is visible at the output 1D.
1A
The address at which port 1 is read or written.
1Din
The data to be stored in the RAM.
2A
The address used to read via port 2.
Outputs
1D
Output Port 1
2D
Output Port 2
Attributes
Data Bits
Number of data bits used.
Address Bits
Number of address bits used.
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.
Program Memory
Makes this ROM to program memory. So it can be accessed by an external IDE.

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A
D Q
we
RAM, async.

9.7. RAM, async.

As long as we is set, it is stored. Corresponds to a very simple RAM, where the address and
data lines are directly connected to the decoders of the memory cells. Exportable to VHDL/
Verilog.
Inputs
A
The address at which reading or writing takes place.
D
The data to be stored.
we
Write enable. As long as this input is set to 1, the value applied to D is stored at the
address applied to A whenever A or D is changed.
Outputs
Q
Output of the stored data.
Attributes
Data Bits
Number of data bits used.
Address Bits
Number of address bits used.
Inverted inputs
You can select the inputs that are to be inverted.
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.
Program Memory
Makes this ROM to program memory. So it can be accessed by an external IDE.

A
str
C D
ld
B
Gr-RAM

9.8. Graphic RAM

Used to show a bitmap graphic. This element behaves like a RAM. In addition it shows its
content on a graphic screen. Every pixel is represented by a memory address. The value
stored defines the color of the pixel, using a fixed color palette. There are two screen buffers

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implemented to support page flipping. The input B selects which buffer is shown. Thus,
the total memory size is dx * dy * 2 words. The palette used is structured as follows: The
indices 0-9 correspond to the colors white, black, red, green, blue, yellow, cyan, magenta,
orange and pink. The indices 32-63 map gray values and the indices 64-127 represent 64
color values each with two bits per color channel. This results in a simple palette that can be
addressed with only 7-bit. If the architecture supports a 16-bit index, from Index 0x8000, a
high-color mode with 5 bits per color channel can be used, which enables 32768 colors.
Inputs
A
The address to read and write.
str
If this input is high when the clock becomes high, the data is stored.
C
Clock
ld
If this input is high the output is activated and the data is visible at the output.
B
Selects the screen buffer to show.
Outputs
D
The bidirectional data connection.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Width in pixels
The screen width in pixels.
Height in pixels
The screen height in pixels.
Rotation
The orientation of the Element in the circuit.

10. Memory - EEPROM

A
CS
D
WE
OE
EEPROM

10.1. EEPROM

A EEPROM module with a bidirectional connection for reading and writing the data. If the CS
input is low, the component is disabled. The data content is stored like in a ROM. It is thus
preserved when the simulation is terminated and restarted. The write cycle works as follows:

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By setting CS to high, the component is selected. A rising edge at WE latches the address,
and the following falling edge at WE stores the data.
Inputs
A
The address to read and write.
CS
If this input is high, this EEPROM is enabled. Otherwise the output is always in high Z
state.
WE
If set to high the data is written to the EEPROM.
OE
If this input is high, the stored value is output.
Outputs
D
The bidirectional data connection.
Attributes
Data Bits
Number of data bits used.
Address Bits
Number of address bits used.
Label
The name of this element.
Inverted inputs
You can select the inputs that are to be inverted.
Data
The values stored in this element.
Rotation
The orientation of the Element in the circuit.
Number Format
The format used to show the numbers.
fixed point digits
Number of fractional binary digits
Program Memory
Makes this ROM to program memory. So it can be accessed by an external IDE.

A
Din
str D
C
ld
EEPROM

10.2. EEPROM, separated Ports

A EEPROM module with separate inputs for storing and output for reading the stored data.

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Inputs
A
The address to read from or write to.
Din
The data to be stored in the EEPROM.
str
If this input is high and when the clock becomes high, the data is stored.
C
Clock input
ld
If this input is high the output is activated and the data is visible at the output.
Outputs
D
The data output pin
Attributes
Data Bits
Number of data bits used.
Address Bits
Number of address bits used.
Label
The name of this element.
Data
The values stored in this element.
Rotation
The orientation of the Element in the circuit.
Number Format
The format used to show the numbers.
fixed point digits
Number of fractional binary digits
Program Memory
Makes this ROM to program memory. So it can be accessed by an external IDE.

11. Memory

D
C Q
en
Reg

11.1. Register

A component to store values. The bit width of the data word can be selected. Unlike a D flip-
flop, the register provides an input which enables the clock. Exportable to VHDL/Verilog.

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Inputs
D
Input pin of the data word to be stored.
C
Clock input. A rising edge stores the value at the D pin.
en
Enable pin. Storing a value works only if this pin is set high.
Outputs
Q
Returns the stored value.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.
Program Counter
Makes this register a program counter. The value of this register is returned to the
external assembler IDE to mark the current line of code during debugging.
Use as measurement value
If set the value is a measurement value and appears in the graph and data table. In
addition, a label must be specified that can serve as identification of the value.

A
D
sel
ROM

11.2. ROM

A non-volatile memory component. The stored data can be edited in the attributes dialog.
Exportable to VHDL/Verilog.
Inputs
A
This pin defines the address of data word to be output.
sel
If the input is high, the output is activated. If it is low, the data output is in high Z state.
Outputs
D
The selected data word if the sel input is high.
Attributes

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Data Bits
Number of data bits used.
Address Bits
Number of address bits used.
Label
The name of this element.
Data
The values stored in this element.
Rotation
The orientation of the Element in the circuit.
Number Format
The format used to show the numbers.
fixed point digits
Number of fractional binary digits
Program Memory
Makes this ROM to program memory. So it can be accessed by an external IDE.
Reload at model start
Reloads the HEX file every time the model is started.
File
File to be loaded into the ROM.
Use big endian at import.
Use big endian byte order at import.

A1 D1
s1 D2
A2
s2
ROM

11.3. ROM dual port

A non-volatile memory component. The stored data can be edited in the attributes dialog.
Inputs
A1
This pin defines the address of data word to be output on D1.
s1
If the input is high, the output D1 is activated. If it is low, the data output is in high Z
state.
A2
This pin defines the address of data word to be output on D2.
s2
If the input is high, the output D2 is activated. If it is low, the data output is in high Z
state.
Outputs
D1
The selected data word if the s1 input is high.
D2
The selected data word if the s2 input is high.

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Attributes
Data Bits
Number of data bits used.
Address Bits
Number of address bits used.
Label
The name of this element.
Data
The values stored in this element.
Rotation
The orientation of the Element in the circuit.
Number Format
The format used to show the numbers.
fixed point digits
Number of fractional binary digits
Program Memory
Makes this ROM to program memory. So it can be accessed by an external IDE.
Reload at model start
Reloads the HEX file every time the model is started.
File
File to be loaded into the ROM.
Use big endian at import.
Use big endian byte order at import.

en out
C ovf
clr
Counter

11.4. Counter

A simple counter component. The clock input increases the counter. Can be reset back to 0
with the clr input. The number of bits can be set in the attribute dialog. Exportable to VHDL/
Verilog.
Inputs
en
If set to 1 the counter is enabled!
C
The clock input. A rising edge increases the counter.
clr
Synchronous reset of the counter if set to 1.
Outputs
out
Returns the counted value.
ovf
Overflow output. This pin is set to 1 if the counter is on its maximal value and the en
input is set to 1.

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Attributes
Data Bits
Number of data bits used.
Inverted inputs
You can select the inputs that are to be inverted.
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.
Use as measurement value
If set the value is a measurement value and appears in the graph and data table. In
addition, a label must be specified that can serve as identification of the value.
Program Counter
Makes this register a program counter. The value of this register is returned to the
external assembler IDE to mark the current line of code during debugging.

en out
C ovf
dir
in
ld
clr
Counter

11.5. Counter with preset

A counter whose value can be set. In addition, a maximum value and a counting direction
can be specified. Exportable to VHDL/Verilog.
Inputs
en
If set to 1 the counter is enabled!
C
The clock input. A rising edge increases or decreases the counter.
dir
Specifies the counting direction. A 0 means upwards.
in
This data word is stored in the counter when ld is set.
ld
If set, the value at input 'in' is stored in the counter at the next clock signal.
clr
Synchronous reset of the counter if set to 1.
Outputs
out
Returns the counted value.
ovf
Overflow output. It is set to 1 if the 'en' input is set to 1 and if the counter reaches its
maximum value when counting up, or has reached 0 when counting down.

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Attributes
Data Bits
Number of data bits used.
Maximum Value
If a zero is entered, the maximum possible value is used (all bits are one).
Inverted inputs
You can select the inputs that are to be inverted.
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.
Use as measurement value
If set the value is a measurement value and appears in the graph and data table. In
addition, a label must be specified that can serve as identification of the value.
Program Counter
Makes this register a program counter. The value of this register is returned to the
external assembler IDE to mark the current line of code during debugging.

S
se
R
ne
C
PRNG

11.6. Random Number Generator

Can be used to generate random numbers. When the simulation is started, the generator is
reinitialized so that a new pseudo-random number sequence is generated at each start. The
generator can be initialized in the running simulation with a defined seed value to generate a
defined pseudo-random number sequence.
Inputs
S
New seed value of the generator.
se
If set, the random number generator is reinitialized with the new seed value at the
next rising clock edge.
ne
If set, a new random number is output at the next rising clock edge.
C
The clock input.
Outputs
R
Output of the pseudorandom number.
Attributes
Data Bits
Number of data bits used.

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Label
The name of this element.
Rotation
The orientation of the Element in the circuit.

12. Arithmetic

a s
b co
ci
Add

12.1. Adder

A component for simple add calculations. Adds the two integer values from input a and input
b (a+b). The result will be incremented by one if the carry input is set. Exportable to VHDL/
Verilog.
Inputs
a
First input to add.
b
Second input to add.
c_i
Carry input, if set the result is incremented by one.
Outputs
s
The result of the addition
c_o
Carry output. If set there was an overflow.
Attributes
Label
The name of this element.
Data Bits
Number of data bits used.
Rotation
The orientation of the Element in the circuit.

a s
b co
ci
Sub

12.2. Subtract

A component for simple subtractions. Subtracts binary numbers on input a and input b (a-b).
If the carry input is set to 1 the result is decremented by 1. Exportable to VHDL/Verilog.

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Inputs
a
Input a for subtraction.
b
Input b for subtraction.
c_i
Carry input, if set the result is decremented by one.
Outputs
s
Output returns the result of the subtraction.
c_o
Output returns 1 if an overflow occurred.
Attributes
Label
The name of this element.
Data Bits
Number of data bits used.
Rotation
The orientation of the Element in the circuit.

a
mul
b
Mul

12.3. Multiply

A component for multiplication. Multiplies the integer numbers on input pin a and input pin b.
Exportable to VHDL/Verilog.
Inputs
a
Input a for multiplication.
b
Input b for multiplication.
Outputs
mul
Output for the result of the multiplication.
Attributes
Label
The name of this element.
Signed Operation
If selected the operation is performed with signed (2th complement) values.
Data Bits
Number of data bits used.

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Rotation
The orientation of the Element in the circuit.

a q
b r
Div

12.4. Division

A component for division. Divides the integer applied to input a by the integer applied to
input b. If the divisor is zero, it is divided by one instead. In signed division, the remainder is
always positive.
Inputs
a
dividend
b
divisor
Outputs
q
quotient
r
remainder
Attributes
Label
The name of this element.
Data Bits
Number of data bits used.
Signed Operation
If selected the operation is performed with signed (2th complement) values.
Remainder always positive
If set, the remainder of a signed division is always positive.
Rotation
The orientation of the Element in the circuit.

in
out
shift
Shift

12.5. Barrel shifter

A component for bit shifting. Shifts the input value by the number of bits given by the shift
input.

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Inputs
in
Input with bits to be shifted.
shift
Input with shift width.
Outputs
out
Output with shifted value.
Attributes
Label
The name of this element.
Data Bits
Number of data bits used.
shift input has sign
shift input data has two complement format
Direction
Set direction.
Mode
Mode of barrel shifter
Rotation
The orientation of the Element in the circuit.

a >
b =
<

12.6. Comparator

A component for comparing bit values. Compares the binary numbers on input pin a and
input pin b and sets the corresponding outputs. Exportable to VHDL/Verilog.
Inputs
a
Input a to compare.
b
Input b to compare.
Outputs
>
Output is 1 if input a is greater than input b
=
Output is 1 if input a equals input b
<
Output is 1 if input a is less than input b
Attributes
Label
The name of this element.

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Data Bits
Number of data bits used.
Signed Operation
If selected the operation is performed with signed (2th complement) values.
Rotation
The orientation of the Element in the circuit.

in out
Neg

12.7. Negation

Negation in the 2th complement Exportable to VHDL/Verilog.

Inputs
in
Input of the data word to be negated in 2th complement
Outputs
out
Returns the result of the negation in 2th complement.
Attributes
Data Bits
Number of data bits used.
Rotation
The orientation of the Element in the circuit.

in out
SignEx

12.8. Sign extender

Increases the bit width of a signed value keeping the values sign. If the input is a single bit,
this bit will be output on all output bits. Exportable to VHDL/Verilog.
Inputs
in
Input value. The input bit width must be smaller than the output bit width!
Outputs
out
Extended input value. The input bit width must be smaller than the output bit width!
Attributes
Label
The name of this element.
Input Bit Width
The number of output bits must be greater than the number of input bits.

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Output Bit Width

The number of output bits must be greater than the number of input bits.
Rotation
The orientation of the Element in the circuit.

in out
Bit count

12.9. Bit counter

Returns the number of 1-bits in the input value.

Inputs
in
The input which 1-bits are counted.
Outputs
out
Outputs the number of 1-bits.
Attributes
Data Bits
Number of data bits used.
Rotation
The orientation of the Element in the circuit.

13. Switches

13.1. Switch

Simple switch. There is no gate delay: A signal change is propagated immediately.

Outputs
A1
One of the connections of the switch.
B1
One of the connections of the switch.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Pole count
Number of poles available.
Closed
Sets the initial state of the switch.

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Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.
Switch behaves like an input
If the model is analyzed, the switch behaves like an input, where "open" corresponds
to '0' and "closed" to '1'.

13.2. Double Throw Switch

Double Throw Switch. There is no gate delay: A signal change is propagated immediately.
Outputs
A1
One of the connections of the switch.
B1
One of the connections of the switch.
C1
One of the connections of the switch.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Pole count
Number of poles available.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.

13.3. Relay

A relay is a switch which can be controlled by a coil. If a current flows through the coil, the
switch is closed or opened. There is no flyback diode so the current direction does not
matter. The switch is actuated if the inputs have different values. The relay behaves similar
to an XOr gate.

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Inputs
in1
One of the inputs to control the relay.
in2
One of the inputs to control the relay.
Outputs
A1
One of the connections of the switch.
B1
One of the connections of the switch.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Pole count
Number of poles available.
Relay is normally closed.
If set the relay is closed if the input is low.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.

13.4. Double Throw Relay

A relay is a switch which can be controlled by a coil. If a current flows through the coil, the
switch is closed or opened. There is no flyback diode so the current direction does not
matter. The switch is actuated if the inputs have different values. The relay behaves similar
to an XOr gate.
Inputs
in1
One of the inputs to control the relay.
in2
One of the inputs to control the relay.

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Outputs
A1
One of the connections of the switch.
B1
One of the connections of the switch.
C1
One of the connections of the switch.
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Pole count
Number of poles available.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.

13.5. P-Channel FET

P-Channel Field Effect Transistor. The bulk is connected to the pos. voltage rail and the
transistor is simulated without a body diode.
Inputs
G
Gate
Outputs
S
Source
D
Drain
Attributes
Data Bits
Number of data bits used.
Unidirectional
Unidirectional transistors propagate a signal only from source to drain. They are much
faster to simulate than bidirectional transistors. Since there is no feedback from drain
to source, in this mode, the transistor can not short the connected wires when it is
conducting. Thus, this mode is necessary to simulate certain CMOS circuits.
Label
The name of this element.

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Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.

13.6. N-Channel FET

N-Channel Field Effect Transistor. The bulk is connected to ground and the transistor is
simulated without a body diode.
Inputs
G
Gate
Outputs
D
Drain
S
Source
Attributes
Data Bits
Number of data bits used.
Unidirectional
Unidirectional transistors propagate a signal only from source to drain. They are much
faster to simulate than bidirectional transistors. Since there is no feedback from drain
to source, in this mode, the transistor can not short the connected wires when it is
conducting. Thus, this mode is necessary to simulate certain CMOS circuits.
Label
The name of this element.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.

13.7. Fuse

A fuse used to build a one time programmable memory.

Outputs
out1
One of the connections of the switch.
out2
One of the connections of the switch.

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Attributes
Programmed
If set a diode is "blown" or "programmed". At a floating gate FET the floating gate is
charged. You can change this setting with the [P] key.
Rotation
The orientation of the Element in the circuit.

13.8. Diode to VDD

A simplified unidirectional diode, used to pull a wire to VDD. It is used to implement a wired
OR. So it is necessary to connect a pull down resistor to the diodes output. In the simulation
the diode behaves like an active gate with a trivalent truth table: If the input high, the output
is also high. In all other cases (input is low or high z) the output is in high z state. So two anti
parallel connected diodes can keep each other in high state, which is not possible with real
diodes. This is an ideal diode: There is no voltage drop across a forward-biased diode.
Inputs
in
If the input is high also the output is high. In all other cases the output is in high z
state.
Outputs
out
If the input is high also the output is high. In all other cases the output is in high z
state.
Attributes
Programmed
If set a diode is "blown" or "programmed". At a floating gate FET the floating gate is
charged. You can change this setting with the [P] key.
Rotation
The orientation of the Element in the circuit.

13.9. Diode to Ground

A simplified unidirectional diode, used to pull a wire to ground. It is used to implement a wired
AND. So it is necessary to connect a pull up resistor to the diodes output. If the input low, the
output is also low. In the other cases (input is high or high z) the output is in high z state. So
two anti parallel connected diodes can keep each other in low state, which is not possible
with real diodes. So this is a ideal diode: There is no voltage drop across a forward-biased
diode.

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 Digital

Inputs
in
If the input is low also the output is low. In all other cases the output is in high z state.
Outputs
out
If the input is low also the output is low. In all other cases the output is in high z state.
Attributes
Programmed
If set a diode is "blown" or "programmed". At a floating gate FET the floating gate is
charged. You can change this setting with the [P] key.
Rotation
The orientation of the Element in the circuit.

13.10. P-Channel floating gate FET

P-Channel Floating Gate Field Effect Transistor. The bulk is connected to ground and the
transistor is simulated without a body diode. If there is a charge stored in the floating gate,
the fet isn't conducting even if the gate is low.
Inputs
G
Gate
Outputs
S
Source
D
Drain
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Programmed
If set a diode is "blown" or "programmed". At a floating gate FET the floating gate is
charged. You can change this setting with the [P] key.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.

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 Digital

13.11. N-Channel floating gate FET

N-Channel Floating Gate Field Effect Transistor. The bulk is connected to ground and the
transistor is simulated without a body diode. If there is a charge stored in the floating gate,
the fet isn't conducting even if the gate is high.
Inputs
G
Gate
Outputs
D
Drain
S
Source
Attributes
Data Bits
Number of data bits used.
Label
The name of this element.
Programmed
If set a diode is "blown" or "programmed". At a floating gate FET the floating gate is
charged. You can change this setting with the [P] key.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.

13.12. Transmission-Gate

A real transmission-gate is build from only two transistors. Therefore, it is often used to save
transistors during implementation on silicon.
Inputs
S
control input.
¬S
inverted control input

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 Digital

Outputs
A
input A
B
input B
Attributes
Data Bits
Number of data bits used.
Rotation
The orientation of the Element in the circuit.

14. Misc.

Test

14.1. Test case

Describes a test case. In a test case you can describe how a circuit should behave. It can
then be automatically checked whether the behavior of the circuit actually corresponds to this
description. If this is not the case, an error message is shown. The help text of the test case
editor describes in detail how such a test case can be created. Exportable to VHDL/Verilog.
Attributes
Label
The name of this element.
Test data
The description of the test case. Details of the syntax can be found in the help dialog
of the test data editor.
Enabled
Enables or disables this component.

15. Misc. - Decoration

Text

15.1. Text

Shows a text in the circuit. Does not affect the simulation. The text can be changed in the
attribute dialog.
Attributes
Description
A short description of this element and its usage.
Font Size
Sets the font size to use for this text.

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 Digital

Rotation
The orientation of the Element in the circuit.
Orientation
Position of the coordinate relative to the text.
Snap To Grid
If set, the component is aligned with the grid.

Text

15.2. Rectangle

Shows a rectangle in the circuit. Does not affect the simulation. If a minus sign is used as the
heading, the heading is omitted.
Attributes
Label
The name of this element.
Width
Width in grid units
Height
Height in grid units
Font Size
Sets the font size to use for this text.
Text Inside
Place text inside the rectangle.
Text at the bottom
Place text at the bottom of the rectangle.
Text on the right
Place text to the right of the rectangle.
Snap To Grid
If set, the component is aligned with the grid.

16. Misc. - Generic

init

16.1. Generic Initialization

Code that is executed to start a generic circuit directly. If a generic circuit is to be started
directly, such a component must be present. Exportable to VHDL/Verilog.
Attributes
Label
The name of this element.
Enabled
Enables or disables this component.

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 Digital

Generic Parameterization
Statements used to generify a circuit.

Code

16.2. Code

Code that is executed when a generic circuit is made concrete. Can be used, for example, to
add components or wires to a circuit. Exportable to VHDL/Verilog.
Attributes
Generic Parameterization
Statements used to generify a circuit.

17. Misc. - VHDL/Verilog

in out
External

17.1. External

Component to execute an external process to calculate the logic function. Is used to specify
the behaviour of a component by VHDL or Verilog. The actual simulation of the behavior
must be done with an external simulator. At present only the VHDL simulator ghdl and the
verilog simulator Icarus Verilog are supported. The label of the component must match the
name of the entity or module! Exportable to VHDL/Verilog.
Inputs
in
Outputs
out
Attributes
Label
The name of this element.
Width
Width of symbol if this circuit is used as an component in an other circuit.
Inputs
The inputs of the external process. It is a comma-separated list of signal names. For
each signal name, a number of bits separated by a colon can be specified. The inputs
of an 8-bit adder could thus be described as "a:8,b:8,c_in".
Outputs
The outputs of the external process. It is a comma-separated list of signal names.
For each signal name, a number of bits separated by a colon can be specified. The
outputs of an 8-bit adder could thus be described as "s:8,c_out".
Program code
The program code to be executed by the external application.

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 Digital

Application
Defines which application to use.
GHDL Options
Options that are used for all processing steps by GHDL.
IVerilog Options
Options that are used for all processing steps by IVerilog.

in out
External File

17.2. External File

Component to execute an external process to calculate the logic function. Is used to specify
the behaviour of a component by VHDL or Verilog. The actual simulation of the behavior
must be done with an external simulator. At present only the VHDL simulator ghdl and the
verilog simulator Icarus Verilog are supported. The label of the component must match the
name of the entity or module! Exportable to VHDL/Verilog.
Inputs
in
Outputs
out
Attributes
Label
The name of this element.
Width
Width of symbol if this circuit is used as an component in an other circuit.
Inputs
The inputs of the external process. It is a comma-separated list of signal names. For
each signal name, a number of bits separated by a colon can be specified. The inputs
of an 8-bit adder could thus be described as "a:8,b:8,c_in".
Outputs
The outputs of the external process. It is a comma-separated list of signal names.
For each signal name, a number of bits separated by a colon can be specified. The
outputs of an 8-bit adder could thus be described as "s:8,c_out".
Program code
The file containing the program code to be executed by the external application.
Application
Defines which application to use.
GHDL Options
Options that are used for all processing steps by GHDL.
IVerilog Options
Options that are used for all processing steps by IVerilog.

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 Digital

17.3. Pin Control

Control logic for a bidirectional pin. This component is necessary only in the context of VHDL
or Verilog generation, in order to create a bidirectional HDL port! If you don't want to use
a bidirectional IO-port on an FPGA, don't use this component! The PinControl component
cannot be used in an embedded circuit! It is only allowed at the top level circuit! Exportable to
VHDL/Verilog.
Inputs
wr
The data to be output.
oe
Activates the output.
Outputs
rd
The data to be read.
pin
The connector for the actual pin. Only a single output should be connected here.
Attributes
Data Bits
Number of data bits used.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.

18. Misc.

VDD
GND
Power

18.1. Power

Has no function. Makes sure that VDD and GND are connected. Can be used in 74xx circuits
to generate the pins for the voltage supply, which are tested for correct wiring.
Inputs
VDD
Must be connected to VDD!
GND
Must be connected to GND!
Attributes

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 Digital

Label
The name of this element.
Rotation
The orientation of the Element in the circuit.

D D0
OE

18.2. Bidirectional Splitter

Can be used for data buses and simplifies especially the construction of memory modules in
a DIL package, as the implementation of the data bus is simplified.
Inputs
OE
When set, the value at the common data terminal D is output to the bit outputs D[i], if
not, the bits D[i] are output to the common output D.
Outputs
D
The common data connection.
D0
The data bit 0 of the bus splitter.
Attributes
Data Bits
Number of data bits used.
Rotation
The orientation of the Element in the circuit.
Mirror
Mirrors the component in the circuit.
Spreading
Configures the spread of the inputs and outputs in the circuit.

18.3. Reset

The output of this component is held high during the initialisation of the circuit. After the
circuit has stabilized the output goes to low. If the output is inverted it behaves the opposite
way. Exportable to VHDL/Verilog.
Outputs
Reset
Reset Output.
Attributes
Label
The name of this element.

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 Digital

Inverted output
If selected the output is inverted.
Rotation
The orientation of the Element in the circuit.

18.4. Break

If this component is used in the circuit, the "Run To Break" button between "Start" and "Stop"
is enabled. This button clocks the circuit until a rising edge on the input of this component is
detected. This element can be used for debugging by clocking the circuit to any breakpoint.
Also an assembler command BRK can be implemented. This allows to execute a program
up to the next BRK command. This function can only be used if the real-time clock is
deactivated!
Inputs
brk
Stops the fast simulation clocking if a rising edge is detected.
Attributes
Label
The name of this element.
Enabled
Enables or disables this component.
Timeout cycles
If this amount of cycles is reached without a break signal, an error is created.
Rotation
The orientation of the Element in the circuit.

stop
Stop

18.5. Stop

A rising edge at the input stops the simulation. Has the same effect as pressing the Stop
button in the toolbar.
Inputs
stop
A rising edge stops the simulation.
Attributes
Label
The name of this element.
Inverted inputs
You can select the inputs that are to be inverted.
Rotation
The orientation of the Element in the circuit.

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 Digital

Async

18.6. Asynchronous Timing

Allows configuration of the timing of an asynchronous sequential circuit such as a Muller-

pipeline. The circuit must be started in single gate step mode and must be able to reach a
stable state at startup. The sequential circuit can then be started interactively or with a reset
gate. It is not allowed to use a regular clock component in this mode.
Attributes
Start real time clock
If enabled the runtime clock is started when the circuit is started
Frequency/Hz
The real time frequency used for the real time clock

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 Digital

E Library
27c801: 8 Mbit (1Mb x 8) UV EPROM
28c010: 1-Megabit (128K x 8) Paged Parallel EEPROM; DATA Polling for End of Write
Detection not implemented!
28c16: 16K (2K x 8) Parallel EEPROM; DATA Polling for End of Write Detection not
implemented!
28c64: 64K (8K x 8) Parallel EEPROM; DATA Polling for End of Write Detection not
implemented!
28c256: 256K (32K x 8) Paged Parallel EEPROM; DATA Polling for End of Write Detection
not implemented!
28c512: 512K-Bit (64K x 8) CMOS Parallel EEPROM; DATA Polling for End of Write
Detection not implemented!
7400: quad 2-input NAND gate
7401: quad 2-input NAND gate with open-collector outputs
7402: quad 2-input NOR gate
7403: quad 2-input NAND gate with open-collector outputs, different pinout than 7401
7404: hex inverter
7405: hex inverter, open-collector output
7406: hex inverter buffer, open-collector output
7407: hex buffer, open-collector output
7408: quad 2-input AND gate
7409: quad 2-input AND gate with open-collector outputs
7410: triple 3-input NAND gate
7411: triple 3-input AND gate
7412: triple 3-input NAND gate with open-collector outputs
7413: dual 4-input NAND gate, Schmitt trigger
7414: hex inverter, Schmitt trigger
7415: triple 3-input AND gate with open-collector outputs
7416: hex inverter buffer, open-collector output, same as 7406
7417: hex buffer, open-collector output, same as 7407
7420: dual 4-input NAND gate
7421: dual 4-input AND gate
7425: dual 4-input NOR gate with strobe
7427: triple 3-input NOR gate
7428: quad 2-input NOR buffer
7430: 8-input NAND gate
7432: quad 2-input OR gate
7440: dual 4-input NAND buffer
7442: 4-line BCD to 10-line decimal decoder
7447: BCD to 7-segment decoder, active low
7448: BCD to 7-segment decoder, active high
7451: 2-input/3-input AND-NOR gate
7454: 2-3-2-3-line AND NOR gate
7455: 2 wide 4-input AND-NOR gate
7458: dual AND OR gate
7474: dual D-flip-flop
7476: dual J-K flip-flops with preset and clear
7480: Gated Full Adder with Complementary Inputs and Complementary Sum Outputs
7482: 2-bit binary full adder

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 Digital

7483: 4-bit binary full adder

7483Real: 4-bit binary full adder, real gates
7485: 4-bit comparator
7486: quad 2-input XOR gate
7489: 64-bit RAM
7490: asynchronous two - five - decimal addition counter
7493: 4-bit Binary Counter. Connect QA to CKB and clock on CKA for full 4-bit counter.
Connect QB to R1 and QD to R2 for a BCD counter.
74107: dual J-K flip-flops with clear
74109: Dual J-NOT-K flip-flop with set and reset; positive-edge-trigger
74112: Dual J-K negative-edge-triggered flip-flop, clear and preset
74116: dual 4-bit D-type latches
74125: Quadruple bus buffer gates with 3-state outputs (active low output enable)
74126: Quadruple bus buffer gates with 3-state outputs (active high output enable)
74133: 13-input NAND gate
74138: 3-line to 8-line decoder/demultiplexer, inverted out
74139: dual 2-line to 4-line decoder/demultiplexer
74147: 10-line to 4-line priority encoder
74148: 8-line to 3-Line priority encoder
74150: 4-line to 16-line data selectors/multiplexers
74151: 3-line to 8-line data selectors/multiplexers
74153: dual 4-line to 1-line data selectors/multiplexers
74154: 4-line to 16-line decoders/demultiplexers
74157: quad 2-line to 1-line data selectors/multiplexers
74160: decimal synchronous counter, async clear
74161: hex synchronous counter, async clear
74162: decimal synchronous counter
74162Real: decimal synchronous counter, real gates
74163: hex synchronous counter
74164: 8-bit parallel-out serial shift register, asynchronous clear
74165: parallel-load 8-bit shift register
74166: 8-Bit Parallel-In/Serial-Out Shift Register
74173: quad 3-state D flip-flop with common clock and reset
74174: hex D-flip-flop
74175: quad D-flip-flop
74181: 4-bit arithmetic logic unit
74182: look-ahead carry generator
74189: 64-Bit Random Access Memory with 3-STATE Outputs
74190: Presettable synchronous 4-bit bcd up/down counter
74191: Presettable synchronous 4-bit binary up/down counter
74193: Synchronous 4-Bit Up/Down Binary Counter with Dual Clock
74194: 4-Bit Bidirectional Universal Shift Register
74194real: 4-Bit Bidirectional Universal Shift Register, Databook implementation.
74198: 8-bit shift register
74238: 3-line to 8-line decoder/demultiplexer
74244: octal 3-state buffer/line driver/line receiver
74245: octal bus transceivers with 3-state outputs
74247: BCD to 7-segment decoder, active low, tails on 6 and 9
74248: BCD to 7-segment decoder, active high, tails on 6 and 9
74253: dual tri state 4-line to 1-line data selectors/multiplexers

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 Digital

74257: quad 2-line to 1-line data selectors/multiplexers (3-state output)

74260: dual 5-input NOR gate
74266: quad 2-input XNOR gate
74273: octal D-type flip-flop with clear
74280: 9 bit Odd-Even Parity Generator-Checker
74283: 4-bit binary full adder, alternative pinning
74299: 8-Input Universal Shift/Storage Register with Common Parallel I/O Pins
74373: octal transparent latches
74374: octal positive-edge-triggered flip-flops
74377: Octal D Flip-Flop with enable
74382: 4-Bit Arithmetic Logic Unit
74540: octal buffer/line driver, inverted
74541: octal buffer/line driver
74573: octal transparent latches, different pinout compared to 74373
74574: octal positive-edge-triggered flip-flops, different pinout compared to 74374
74590: 8-bit binary counter with tri-state output registers
74595: 8-Bit Shift Registers with 3-State Output Registers
74670: 3-state 4-by-4 Register File
74682: 8-bit digital comparator
74688: 8-bit identity comparator
74779: 8-Bit Bidirectional Binary Counter with 3-STATE Outputs
74804: hex 2-input NAND gate https://www.ti.com/lit/ds/symlink/sn74as804b.pdf
74805: hex 2-input NOR gate http://www.ti.com/lit/ds/symlink/sn54as805b.pdf
74808: hex 2-input AND gate http://www.ti.com/lit/ds/symlink/sn54as808b.pdf
74832: hex 2-input OR gate http://www.ti.com/lit/ds/symlink/sn54as832b.pdf
744002: dual 4-input NOR gate
744017: Johnson decade counter with 10 decoded outputs
744075: triple 3-input OR gate
7440105: 4-Bit x 16-Word FIFO Register
A623308A: 8K X 8 BIT CMOS SRAM
RAM32Bit: Ein 32-Bit-Speicher, der Bytezugriff ermöglicht und auch mit nicht
ausgerichteten Speicheradressen umgehen kann.

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