CPE325 GROUP 3

MULTIPROCESSOR SYSTEMS

Definition; A multiprocessor system is a computer system with two or more

processors (CPU) that work together to execute tasks efficiently, unlike single-
processor system where tasks are executed sequentially….. It is an
interconnection between two or more cpu, with memory an input-output
equipment

Types of microprocessor systems

Multiprocessor systems can be classified into different types based on their

architecture and memory access methods. Here are the main types:

1. Symmetric Multiprocessing (SMP); is a type of multiprocessor system

where two or more identical processors share a single memory and
operate under a unified operating system. In SMP systems, all
processors have equal access to resources and can execute tasks
independently, enhancing performance and efficiency.

Key Features of SMP

 All processors share the same memory and operate under a single OS.
 Each processor has equal access to resources and can perform tasks
independently.
 Common in modern multi-core processors.

2. Asymmetric Multiprocessing (AMP); is a type of multiprocessor system

where processors do not have equal roles. Instead, one processor (the
master) controls the system, while the other processors (slaves) handle
specific tasks assigned by the master.

Key Features of AMP

 One processor (master) controls the system, while others (slaves) handle
specific tasks.
 Used in specialized applications where certain processors are optimized
for specific function

1
 3. Massively Parallel Processing (MPP); Massively Parallel Processing
(MPP) is a type of computing architecture where many processors work
simultaneously on different parts of a computational task. Each
processor in an MPP system has its own memory and communicates
with others through a high-speed network.

Key Features of AMP

 Fast data processing

Examples of Microprocessor System

Here are some examples

Supercomputers:

Supercomputers often use numerous processors working together to solve

complex problems.

Servers:

Many servers utilize multiple processors to handle numerous simultaneous

requests.

Modern PCs and Laptops:

Modern processors often include multiple cores (which are essentially

processors) to improve performance and multitasking abilities.

In essence, a multiprocessor system leverages the power of multiple CPUs to

perform tasks concurrently, resulting in improved performance, reliability,
and scalability compared to single-processor systems.

DIRECT MEMORY ACCESS (DMA)

Subtitle: Optimizing data transfer for performance

Speaker Notes:

2
Today, I’ll be talking about Direct Memory Access, or DMA—a key system
that improves how computers handle data transfers between hardware and
memory.

WHAT IS DMA?

Content:

DMA allows hardware to transfer data directly to or from memory

Bypasses the CPU during the transfer

Increases system performance

Speaker Notes:

DMA enables hardware like disk drives or network cards to transfer data
directly to or from system memory. This happens without the CPU managing
every step, freeing it up to perform other tasks and improving system
efficiency.

WHY DMA MATTERS

Content:

Efficiency: Reduces CPU workload

Speed: Faster than CPU-controlled transfers

Multitasking: Enables better parallel processing

SPEAKER NOTES:

The main advantage of DMA is that it lightens the load on the CPU. With less
CPU involvement, the system can move data faster and handle multiple
operations at once.

TYPES OF DMA

Content:

3
Burst Mode

Cycle Stealing Mode

Transparent Mode

Speaker Notes:

DMA comes in three main types, each balancing speed and CPU access
differently. Let’s look at each one briefly.

BURST MODE

Content:

Transfers a large block of data all at once

Temporarily halts CPU access to memory

Very fast

Speaker Notes:

In burst mode, a whole chunk of data is sent in one go. This makes it fast, but
during that time, the CPU can't access memory, which might slow down some
other tasks.

CYCLE STEALING MODE

Content:

Sends data in small chunks

CPU and DMA share memory access

Balanced performance

4
Speaker Notes:Cycle stealing allows the CPU and DMA to share memory
access by alternating control. It’s not as fast as burst mode, but it keeps the
system responsive.

TRANSPARENT MODE

Content:

DMA works only when the CPU is idle

Avoids interrupting the CPU

Slowest but least disruptive

Speaker Notes:

This mode waits until the CPU is idle before transferring data, ensuring no
disruption. It’s the slowest but ideal when smooth CPU operation is critical.

WHERE IS DMA USED?

Content:

Hard drives

Sound cards

Graphics cards

Network cards

Speaker Notes:

DMA is commonly used in devices that need to move lots of data quickly—like
hard drives for file access, sound cards for audio playback, and graphics or
network cards for video and internet data.

FINAL THOUGHTS

5
Content:

DMA optimizes data flow between devices and memory

Improves system speed and multitasking

Essential for modern computing

Speaker Notes:

To wrap up, DMA is a behind-the-scenes hero that helps systems run

smoother and faster. It ensures that high-speed data transfers don’t get in the
way of overall performance.

BITSLICE MICROCOMPUTERS

Bitslice microcomputers are a fascinating part of computing history where

engineers quite literally built their own CPUs using modular components.
Instead of relying on a single-chip processor, they used multiple small chips—
each handling just a few bits of data—to form a complete, custom CPU. This
approach was widely used in the 1970s and early 1980s.

How Bitslice Works

A bitslice processor handles a "slice" of data—typically 1, 2, 4, or 8 bits.

These slices are like puzzle pieces. Engineers would combine multiple slices in
parallel to process wider data words (e.g., 16-bit, 32-bit, or more). Each slice
typically included part of the ALU (Arithmetic Logic Unit), registers, and
control logic.

The brain of a bitslice system was often a separate microcode controller.

Engineers wrote their own microcode to define how the CPU should behave—
offering tons of flexibility but requiring detailed knowledge of digital design.

6
Key Features

Highly Customizable: Bitslice systems let engineers build CPUs tailored to

specific applications, whether for math-heavy tasks or unusual data formats.

Scalable Data Widths: Need a 20-bit or 48-bit CPU? Just stack more slices
together.

Microcoded Control: Designers could create their own instruction sets by

writing microcode, making the processor behave exactly as needed.

Examples

AMD 2900 Series: Especially the AM2901 4-bit slice—hugely popular for
custom CPU designs.

Intel 3000 Series: Intel’s take on bitslice components.

DEC VAX 11/780: A famous computer that used bitslice architecture for part
of its CPU.

National Semiconductor IMP-16: One of the earlier modular processor

examples.

Applications

7
Bitslice microcomputers were used in systems that demanded speed and
precision, including:

Scientific and industrial control systems

Military and aerospace computing

Early signal processing hardware

Custom math or graphics processors

SOFTWARE CONSIDERATION AND REQUIREMENTS

Software Consideration involves evaluating and planning various factors that

influence the success of a software project. These include selecting the right
development tools, frameworks, and technologies based on the project scope
and objectives. Important aspects to consider are software architecture,
compatibility with existing systems, scalability, performance, maintainability,
and ease of integration. Decisions made at this stage significantly impact the
software's long-term reliability and cost-effectiveness.

Key software considerations include:

* Platform Choice: Whether the software will run on web, desktop, mobile, or
multiple platforms.

* Technology Stack: Selecting suitable programming languages, databases,

and frameworks.

* Security: Planning for data protection, user authentication, and secure

coding practices.

8
* Future Maintenance: Ensuring the software can be easily updated or scaled
as requirements evolve.

Software Requirements define what the software system must accomplish and
under what conditions it must operate. These are gathered through
interaction with stakeholders and are essential for guiding the design,
development, and testing phases.

Types of software requirements:

1. Functional Requirements: Describe specific functions the system should

perform, such as login, file upload, or generating reports.

2. Non-Functional Requirements: Define quality attributes like performance,

security, usability, reliability, and response time.

3. User Requirements: Focus on the end-user's needs and the tasks they need
to perform using the software.

4. System Requirements: Specify the hardware, software, and network

configurations necessary to run the system effectively.

Clearly defined requirements help avoid scope creep, ensure user satisfaction,
and lead to the development of a more robust and effective software solution.

RISC AND CISC

 A computer processor will have an instruction set that it can use to
execute programs
 This will vary from one processor to the next
9
  There are 2 types of processors:
 Complex Instruction Set Computer
 Reduced Instruction Set Computer
RISC (Reduced Instruction Set Computer)
 Reduced Instruction Set Computer (RISC) consists of a smaller
instruction set with more simple instructions
 Each instruction takes one clock cycle to execute which makes it
more suitable for pipelining
 Compilers are more complicated so will generate more instructions
 Has fewer addressing modes
 Is usually used in smartphones and tablets
CISC (Complex Instruction Set Computer)
 Complex Instruction Set Computer (CISC) consists of a larger
instruction set which includes more complex instructions
 As the instructions are more complex, they can take more than one
clock cycle to execute
 Has more general purpose registers
 Instructions take up less space in memory
 Is usually used in laptops and desktop computers What’s the difference
between RISC & CISC?

RISC CISC

Feature Has fewer transistors Has more transistors

Takes one clock cycle per Takes multiple clock cycles per
instruction instruction

Suited to pipelining Not suited to pipelining

Compilers are more

Compilers are less complicated
complicated

Has fewer general purpose Has more general purpose

10
 registers registers

Used in smartphones and

Used in laptops and desktops
tablets

Has fewer addressing

Has more addressing modes
modes

Requires less power Requires more power

Benefits / Costs less to manufacture Costs more to manufacture

Drawbacks
Takes up more space in
Takes up less space in memory
memory

 A program that has been written for a RISC processor won’t work on a
CISC processor and vice versa
A program that has been written for a RISC processor won’t necessarily work on
another RISC processor as they may have different instruction sets.

SERIAL AND PARALLEL I/O INTERFACE

An I/O interface (or device interface) controls the operation of a peripheral

device according to commands. Serial and parallel I/O interfaces are the two
different ways used to connect devices to microcontrollers and computers for
data transfer.

Serial interfaces transmit data one bit at a time over a single wire or channel.
To connect an electronic system to an external device such as a PC or
instrumentation, serial I/O is often preferred because it reduces the amount of
wiring required. Among the serial I/O standards available for use today are:

USB

I2S (inter-IC sound bus)

I2C (inter-IC bus)

SPI (serial peripheral interface)

Serial ATA
11
Bluetooth (wireless)

Wi-Fi (wireless)

Advantages of serial I/O interface

1. Fewer Wires Needed : Only requires a few lines making the wiring
simpler and cheaper compared to parallel interfaces.

2. Requires less hardware compared to parallel interfaces, which helps

reduce manufacturing and maintenance costs.

3. Ideal for long-distance data transmission because fewer wires reduce

signal interference and degradation.

4. Compact Design :Useful in compact devices where space for wiring and
connectors is limited (e.g., embedded systems, mobile devices).

Disadvantages of serial I/O interface

1. Slower data transfer: Serial transmission sends data one bit at a time,
which can be slower than parallel communication for short distances.

2.More Complex Protocols: Protocols like I2C or SPI may require additional
logic for addressing, acknowledgment, or synchronization, especially in multi-
device systems.

3.Not Ideal for High-Speed Local Transfer: For very high-speed or high-
volume data (like video streaming or memory access), serial may not be
efficient compared to parallel methods.

Applications of the serial I/O interface

12
1. Computer Peripherals: Devices like mice, keyboards, and printers
(especially via USB) use serial protocols.

2. Communication Networks: For transmitting data over long distances in

networks, as they are more cost-effective than parallel communication for
longer cables.

3. Industrial Automation: it’s used for connecting computers to

Programmable Logic Controllers (PLCs) in industrial automation systems.

Parallel interfaces transmit multiple bits simultaneously over multiple wire or

channels

In early versions of the microprocessor, data was grouped into bytes (8 bits).
Today, microprocessors work with 8, 16, 32, 64, and 128 bits of data. Access to
more memory requires address buses with an increased number of bits and
the required control signals. The variety of parallel I/O standards available
for use today include:

• Centronics (PC printer port)

• IEEE 488-1975 (also known as GPIB, general purpose instrument bus)

• SCSI (small computer system interface)

• IDE (integrated drive electronics)

• ATA (AT attachment)

Centronics is primarily used for printers, IEEE 488 (GPIB) connects

instruments and computers in automation systems, SCSI is used for
connecting various peripherals like hard drives, IDE/ATA connects hard
drives and other storage devices to the computer, and ATA connects hard
drives.

Advantages of Parallel Interface

13
1. Multiple bits are transmitted simultaneously, leading to faster data
transmission over short distances.

2. Parallel interfaces are typically less complex in protocol design

compared to serial interfaces.

3. Efficient for Short Distance Communication: Ideal for high-speed data

exchange between closely located devices (e.g., internal computer components)

4. Multiple data lines allow concurrent transmission, which increases

throughput

Disadvantages of Parallel Interface

1. Limited Distance: Signal degradation and crosstalk occur over long

distances due to parallel lines interfering with each other.

2. More Cables and Pins Required: Needs multiple lines for data, control,
and ground, which increases cable bulk and connector size.

3. Synchronization Issues: Keeping multiple lines perfectly in sync (timing

skew) becomes difficult as speed or distance increases.

4. Higher Cost :More wires and connectors mean higher material and
manufacturing costs.

Application of parallel I/O interface

1. Microcontrollers and Embedded Systems

• Parallel ports (like GPIO ports) control LEDs, motors, sensors, and
displays.

• Used for reading multiple switches or controlling multiple actuators at

once.

2. Printers (especially older ones)

• Early printers used parallel ports (like the Centronics interface) for fast
data transfer from computers.
14
3. Data Acquisition Systems

• In laboratory and industrial setups, parallel I/O helps capture multiple

sensor readings simultaneously.

4. Industrial Automation

• Parallel I/O modules control multiple machines and read sensors at the
same time for quick real-time response.

Peripheral Interface Adapter (PIA)

A Peripheral Interface Adapter (PIA) is a digital device used to allow a

microprocessor to
communicate with external peripheral devices such as displays, keyboards,
printers, or other I/O
devices. It serves as an interface between the central processing unit (CPU)
and these external
components, facilitating smooth data exchange.
Function and Purpose
The PIA is designed to manage parallel data transfer between a
microprocessor and external
hardware. It extends the I/O capabilities of the microprocessor by providing
additional ports and
control lines. It can handle both input and output operations and supports
interrupt-driven as well as
polled communication.
Main Components of a PIA
1. Two 8-bit Bidirectional I/O Ports (Port A and Port B):
Each port has 8 data lines, which can be programmed as either input or
output lines. This allows
the PIA to send or receive 8 bits of data simultaneously.
2. Control Lines (CA1, CA2 for Port A and CB1, CB2 for Port B):
These are used for handshaking between the PIA and peripheral devices.
They help synchronize
data transfers and can generate interrupts to alert the CPU.
3. Data Direction Registers (DDR):
These registers define whether each line of a port is configured as an input or
an output. Thisallows for flexible and dynamic control of data direction.
4. Control Registers:

15
These are used to configure the behavior of the ports and control lines. They
enable features like
interrupt control, handshake modes, and strobe signal configuration.
5. Data Bus Buffer:
This internal buffer connects the PIA to the system's data bus. It allows the
microprocessor to
write data to or read data from the PIA.
Working Principle
The PIA is connected to the system bus of a microprocessor. When the
microprocessor wants to
send or receive data from a peripheral, it accesses the PIA through read or
write operations.
- In output mode, the CPU sends data to the PIA, which then passes it to the
peripheral device.
- In input mode, the peripheral sends data to the PIA, and the CPU reads it
when ready.
- Control lines can be used to indicate when data is available or when a
transfer is complete. They
can also trigger interrupts for more efficient communication.
Modes of Operation
1. Input Mode: Data flows from the peripheral into the microprocessor via the
PIA.
2. Output Mode: Data is sent from the microprocessor to the peripheral
through the PIA.
3. Handshake Mode: Control lines are used to synchronize the data transfer
process.
4. Interrupt Mode: The PIA can signal the microprocessor when data is
ready, reducing the need for
constant polling.Example: Motorola MC6821
The MC6821 is a commonly used PIA developed by Motorola. It features:
- Two 8-bit ports (Port A and B)
- Four control lines (CA1, CA2, CB1, CB2)
- Compatibility with Motorola 6800-series microprocessors
- Widely used in early computing and embedded applications
Applications
- Interfacing keyboards and LED displays
- Communication with printers
- Control of motors and relays in automation systems
- Data acquisition systems in embedded electronics
Advantages
16
- Provides flexible and programmable I/O options
- Simple to interface with microprocessors
- Supports both polled and interrupt-driven data transfer
- Easy to use in educational and prototype systems
Limitations
- Limited to 16 I/O lines (8 per port)
- Lacks high-speed communication capabilities- Considered obsolete in
modern systems, replaced by more advanced interfaces like SPI, I2C, and
USB
Conclusion
The Peripheral Interface Adapter is a foundational component in early
microprocessor systems.
While newer technologies have largely replaced it in modern designs,
understanding the PIA is
crucial for grasping how microprocessors interact with the external world. Its
simple yet powerful

design offers valuable lessons in digital communication and embedded

systems.

DIRECT MEMORY ACCESS

WHAT IS DIRECT MEMORY ACCESS (DMA)?

Direct Memory Access, or DMA, is a method computers use to move data

between devices (like hard drives or graphics cards) and the computer’s
memory (RAM) without constantly involving the CPU. This helps make things
faster and frees up the CPU to do other tasks.

---

How does DMA work?

Here’s a simple breakdown of the steps:

1. Requesting a Transfer: A device (like a hard drive) asks the DMA

controller to start moving data.

17
2. Setting Things Up: The DMA controller prepares by deciding where to get
the data from, where to send it, how much data to move, and whether it’s
reading or writing.

3. Data Transfer: The DMA controller takes over the data bus and starts
moving the data directly between the device and memory.

4. Finishing Up: Once the transfer is done, the DMA controller tells the CPU
that everything is complete.

---

Why use DMA?

Faster transfers: DMA can move data more quickly than if the CPU had to do
it.

Less work for the CPU: The CPU can focus on more important jobs instead of
wasting time on data transfers.

Better efficiency: It’s especially useful when large amounts of data need to be
moved.

---

TYPES OF DMA:

Single-channel DMA: One device uses one dedicated DMA channel.

18
Multi-channel DMA: Several devices can share a single DMA controller, each
using its own channel.

---

Where is DMA used?

Disk operations: Moving data between your hard drive or SSD and RAM.

Network activity: Handling data from your network card to memory.

Graphics: Transferring images or video data from memory to the graphics

card.

---

Any downsides?

Bus sharing: The DMA and CPU might compete for access to memory, which
can slow things down.

Setup cost: Setting up DMA transfers takes some effort, so it might not be
worth it for small data movements.

---

In short:

DMA is a smart way for computers to move data around quickly and
efficiently without overloading the CPU. It’s especially handy for large or
frequent transfers, like loading files, streaming video, or handling
network traffic.

19
1. Introduction to DMA (Direct Memory Access)

- WHAT IS DMA?

DMA stands for Direct Memory Access. It’s a way for devices (like a USB
drive, hard disk, or sound card) to move data directly to or from the
computer's memory without always bothering the CPU.

- WHY IS DMA IMPORTANT?

Normally, the CPU has to copy data from a device to memory or from
memory to a device. This takes time and slows things down. DMA lets the
device do it itself — faster and more efficient.

- WHY DO WE USE DMA (THE MOTIVATION)?

Imagine you’re trying to copy a huge file. If the CPU had to handle every step,
it would get too busy and couldn’t do anything else. DMA helps by:

Saving time (data is moved faster)

Letting the CPU rest or focus on other tasks

Making the whole system work better.

2. How DMA Works

- BASIC IDEA:

Imagine you're the CPU, and your job is to manage everything in the
computer. Now, if every time a file needed to be moved, you had to do it
yourself, you’d be too busy to do anything else. So, you hire an assistant —
that assistant is the DMA Controller (DMAC).

- DMA vs CPU Data Transfer:

Without DMA (old way):

The CPU handles every step of moving data between memory and devices. It’s
like the boss doing the cleaning.

With DMA:

20
The DMAC (assistant) handles the data moving, so the boss (CPU) can focus
on more important things — like running programs.

What is the DMA Controller (DMAC)?

This is a special chip or circuit that controls the DMA process. It knows where
the data is coming from, where it's going, and how much to move. It's like a
smart delivery guy.

Steps in a DMA Transfer:

I)CPU Sets It Up:

The CPU tells the DMAC where the data is, where to send it, and how much
to move (like giving delivery instructions)

II)DMA Controller Takes Over:

The DMAC says, “I got this,” and starts the data transfer without bothering
the CPU.

III)Direct Transfer Happens:

Data moves straight from the device to memory (or the other way around). No
CPU help needed.

IV)DMA Interrupts the CPU When Done:

When the data is fully transferred, the DMAC sends a little signal (called an
interrupt) to tell the CPU: “All done!”

3. Modes of DMA Operation

DMA can work in different “styles” or modes depending on how much control
it takes and how it shares time with the CPU.

I)Burst Mode (Block Transfer)

HOW IT WORKS:

DMA grabs the entire bus (the data road) and transfers a big block of data all
at once without stopping.

21
Example: Like a truck using the whole highway to carry a huge shipment in
one trip.

Advantage: Super fast for big data transfers.

Disadvantage: The CPU can’t use the bus while DMA is working — it has to
wait.

II) Cycle Stealing Mode

How it works:

DMA takes small time slots in between CPU operations to transfer data.

Example: Like a kid borrowing your pencil for just a second between your
writing — over and over.

Advantage: CPU and DMA can kind of share the bus.

Disadvantage: Slower than Burst Mode because DMA is always pausing.

III)Transparent Mode (Hidden DMA)

How it works:

DMA only transfers data when the CPU isn’t using the bus at all — it stays
completely out of the CPU’s way.

Example: Like cleaning a room only when no one’s inside — super polite and
quiet.

Advantage: CPU never notices; smooth operation.

Disadvantage: Can be very slow if the CPU is always busy.

Each mode is used depending on what’s more important: speed or keeping the
CPU free.

4. Benefits of DMA

DMA makes the computer faster, smarter, and more efficient by handling
data transfers in the background. Here's how:

22
I)Reduces CPU Overhead

What this means:

The CPU doesn’t have to spend time moving data around.

Why it's good:

It can focus on running programs and doing calculations, which makes

everything smoother.

II)Faster Data Transfer Rates

Why:

DMA moves data directly between memory and devices — no middleman

(CPU) slowing it down.

Result:

Data moves faster, especially with things like big files or video streams.

III) Improves Overall System Performance

How:

With DMA handling transfers and the CPU focusing on other jobs, the whole
system works better.

Especially helpful for:

Devices that move lots of data, like hard drives, sound cards, and graphics
cards.

Bottom line, DMA makes computers work smarter, not harder.

5. Applications of DMA

DMA is super useful wherever a lot of data needs to be moved quickly,

especially without slowing down the CPU. Let’s look at some real examples:

I)Disk Drives (SSD/HDD)

23
What happens:

When you open a file or save something, the data moves between your disk
and RAM.

How DMA helps:

It moves the file directly without making the CPU do it — which means faster
loading and saving.

II). Graphics Cards (GPU Memory Access)

What happens:

Games and videos use a lot of images and data. This info has to move quickly
to the graphics card.

How DMA helps:

DMA transfers game textures, frames, or effects straight into GPU memory,
keeping things smooth and fast.

III) Network Interface Cards (NICs)

What happens:

These cards handle internet or network data.

How DMA helps:

It directly transfers data packets between memory and the network card
without CPU delay — which helps in faster downloading, uploading, or online
gaming.

IV). Audio/Video Streaming

What happens:When you watch a video or listen to music, data needs to

stream smoothly.

How DMA helps:

24
It transfers audio/video data in real time without interrupting the CPU — no
lag, no stuttering.

DMA is basically like the silent superhero in computers — it works behind the
scenes to keep things fast and smooth.

6. Challenges and Limitations

Even though DMA is awesome, it’s not flawless. Here are some of the main
problems:

I) Bus Contention

What this means:

Both the CPU and DMA may try to use the same data bus (like a shared road)
at the same time.

Problem:

They can get in each other’s way, slowing things down — especially during
heavy data movement

II) Security Risks (DMA Attacks)

What this means:

Since DMA can access memory directly, hackers can use it to read or change
data without the CPU noticing.

Example:

A malicious device (like a fake USB or Thunderbolt cable) could plug in and
secretly read your memory — this is called a DMA Attack.

III). Complexity in Implementation

What this means:

Setting up DMA needs extra hardware and software work. It’s more
complicated than just letting the CPU do the job.

25
Result:

It can be harder to design, test, and troubleshoot systems that use DMA,
especially for beginners or small embedded devices.

So, while DMA is powerful, it has its own risks and challenges — just like any
tool. Still, with good design, it’s usually worth it.

7. DMA in Modern Systems

DMA is not just an old-school trick — it’s still very important in today’s
advanced devices. Here’s how it fits into modern technology:

I)Use in Multi-Core Processors

What this means:

Today’s CPUs have multiple cores (like several brains in one chip).

How DMA helps:

Instead of all cores waiting for data, DMA feeds data to memory quickly,
keeping all cores busy and working efficiently.

II) Integration with Modern I/O Technologies (PCIe, NVMe)

PCIe (Peripheral Component Interconnect Express):

Used to connect fast devices like GPUs and SSDs.

NVMe (Non-Volatile Memory Express):

A super-fast way to connect SSDs.

How DMA fits in:

These systems use DMA to move data quickly without slowing down the CPU,
allowing for super-fast file transfers and performances.

III)Role in Embedded Systems and IoT Devices

Embedded systems:

26
Small computers inside things like washing machines, robots, and car engines.

IoT (Internet of Things):

Smart devices like smartwatches, smart fridges, etc.

Why DMA is useful:

These devices have limited processing power, so DMA helps by handling data
transfers efficiently, letting the small CPU focus on other tasks.

So , in today’s high-tech world — from powerful PCs to tiny smart devices —

DMA continues to be a key player for speed and efficiency

MICROCOMPUTER INTERFACE AND PROGRAMMABLE

PERIPHERAL INTERFACE

A microcomputer interface refers to the way a microcomputer communicates

and interacts with external devices, known as peripherals. These peripherals
can include input devices like keyboards and mice, output devices like
monitors and printers, and other components like memory and storage.

Key aspects of microcomputer interfacing include:

* Physical Connections: This involves the physical cables, connectors, and

pins used to link the microcomputer to the peripheral. Different standards
like USB, HDMI, serial, and parallel interfaces exist.

* Electrical Signaling: This defines the voltage levels, timing, and protocols
used to transmit data and control signals between the microcomputer and the
peripheral.

* Logical Protocols: These are the rules and procedures that govern the
exchange of information, ensuring that data is correctly interpreted by both
the microcomputer and the peripheral.

27
 * Software Drivers: These are programs that allow the microcomputer's
operating system to understand and communicate with specific peripheral
devices.

A programmable peripheral interface (PPI) is a specialized integrated circuit

(IC) designed to provide flexible parallel input/output (I/O) capabilities for
microcomputer systems. Instead of having fixed input or output lines, a PPI
can be configured through software to define individual pins or groups of pins
as either inputs or outputs.

The Intel 8255A is a very common and widely used PPI chip. It provides 24
I/O lines that are grouped into three 8-bit ports (Port A, Port B, and Port C).
These ports can be programmed in various modes to support different I/O
configurations and data transfer methods.

Key features of a PPI like the 8255A include:

* Programmable Port Configuration: Each port or groups of bits within a

port can be independently set as an input or an output.

* Operating Modes: PPIs often offer different operating modes to handle

various I/O requirements, such as simple I/O, handshaking for synchronized
data transfer, and bidirectional data communication. For example, the 8255A
has Mode 0 (simple I/O), Mode 1 (strobed I/O with handshaking), and Mode 2
(bidirectional bus).

* Control Register: The functionality of the PPI is configured by writing a

control word into a dedicated control register. This control word specifies the
mode of operation for each port and the direction of data flow.

* Interfacing with the Microcomputer: The PPI connects to the

microcomputer's data bus, address bus, and control signals, allowing the CPU
to read data from input ports, write data to output ports, and configure the
PPI's operation.

In essence, a PPI simplifies the interfacing of parallel I/O devices to a

microcomputer system by providing a flexible and software-configurable
interface. Instead of designing complex external logic circuits for each
peripheral, the designer can program the PPI to meet the specific I/O
requirements of different devices. This makes the system more adaptable and
easier to modify.

28
Examples of how PPIs are used in microcomputer interfacing:

* Keyboard and Display Interfacing: A PPI can be used to read data from a
keyboard and send data to a display.

* Data Acquisition Systems: Connecting analog-to-digital converters (ADCs)

and digital-to-analog converters (DACs) to a microcomputer for data
acquisition and control applications.

* Motor Control: Generating control signals to drive stepper motors or other

types of motors.

* Interfacing with Sensors and Actuators: Reading data from sensors and
controlling actuators in embedded systems.

* Parallel Data Transfer: Transferring data between the microcomputer and

external devices that communicate using parallel interfaces.

In essence, the interaction between a microcomputer and the external world

hinges on interfacing. This involves establishing effective communication
pathways that allow the microcomputer to control and exchange data with a
diverse range of peripheral devices.

TIMING AND INTERRUPT

Key Points:

Interrupts in microcomputers temporarily pause programs to handle urgent

tasks, like responding to device inputs.

Timing involves using internal timers to measure and control when operations
occur, ensuring precision in real-time systems.

timers and interrupts work together for efficient, responsive operations, such
as periodic tasks like LED blinking.

The evidence leans toward interrupts being essential for managing time-
sensitive events, though complexity varies by system.

Timing Mechanisms in Microcomputers

29
Timing in microcomputers involves managing when operations occur, often
facilitated by internal timers. These are hardware components that measure
time intervals by incrementing a counter at a frequency based on the system
clock. Timers can be configured to trigger events or generate interrupts when
a specific count is reached, enabling precise control over operations like
delays, periodic signals, or measuring external event durations.

Internal timers offer several advantages over software-based delay functions,

as highlighted in Internal Timers and Interrupts. They provide precise timing,
as they are hardware-based and not subject to execution time variations. They
are also power-efficient, allowing the microcomputer to enter low-power
modes while the timer runs in the background, and they support multitasking
by freeing the processor for other tasks, unlike blocking delay functions.

For example, in real-time systems, timers are used for periodic tasks such as
sampling an Analog-to-Digital Converter (ADC) 100 times per second, which
requires interrupts every 10 milliseconds. The SysTick timer, commonly
found in ARM Cortex-M microcontrollers, is a specific implementation for
periodic interrupts, with detailed register settings (e.g., NVIC_ST_CTRL_R,
NVIC_ST_RELOAD_R) The frequency calculation, Frequency = f_BUS /
(n+1), where n is the reload value and f_BUS is the bus clock frequency,
ensures precise timing, with examples given for 80 MHz and 16 MHz clocks.

How Does Timing Work?

Timing in microcomputers uses internal timers, hardware components that

count time based on the system clock. These timers can trigger events at
precise moments, like updating a display every second, ensuring accurate and
efficient operation.

Interrupt

Interrupts ensure time-sensitive tasks are handled promptly, avoiding

constant polling, which is key for real-time systems.

They come in hardware types, like button presses, and software types, such as
system calls for exceptions.

When an interrupt occurs, the microprocessor saves its state, jumps to the
ISR, executes it, then resumes the original program.This process minimizes

30
latency, ensuring quick responses, which is crucial for efficient
microcomputer operations.

Interrupts sync software and hardware, managing speed differences, like

software taking 1 microsecond versus hardware's 1 millisecond.

Five conditions must be met for an interrupt, including arming the device and
enabling global interrupts.

• Interrupts let processors react fast to events, vital for timing-sensitive

tasks in microcomputers.

• Interrupt latency is the delay from generation to handling, key for

understanding system timing.

• These are split into software interrupts, like system calls, and hardware
ones, triggered by devices.

• Internal timers measure time intervals and trigger events at specific

times, using a counter tied to the system clock.

• They offer precise timing, better power efficiency, and multitasking

compared to delay functions.It includes code examples for the ATmega2560,
showing timers and interrupts in action, like blinking an LED every second or
two (Medium).

I'm thinking this practical example could really help illustrate how timing
works in microcomputers.Timing in microcomputers often involves managing
when operations occur, such as reading sensors or updating displays.

Timers are essential for creating delays or synchronizing with external events,
improving system efficiency.

Using timers with interrupts lets the microcomputer handle other tasks while
waiting, which is pretty handy.Interrupts are signals that temporarily halt the
normal execution of a program to handle specific events or tasks.They allow
the microprocessor to respond quickly to external or internal events, such as
input from peripherals or timer expirations.

What Are Interrupts?

31
Interrupts are signals that allow a microcomputer to pause its current task
and handle urgent events, such as a keyboard press or sensor data. This
ensures quick responses without constant checking, which is vital for real-time
systems.

Timers are more accurate than software-based delays, which can vary due to
execution time.

They allow the microcomputer to enter low-power modes while waiting for a
timer event.

A practical example is blinking an LED at 1 Hz using a timer interrupt,

showing how timing works in action.

Introduction to Interrupts

Interrupts are fundamental to microcomputer operation, enabling the

processor to respond promptly to asynchronous events. An interrupt is a
signal that temporarily halts the current program execution to address a
specific task, such as handling input from a peripheral device (e.g., a
keyboard or sensor) or an internal event like a timer expiration. This
mechanism is essential for real-time systems, where delays could lead to
system failures or inefficiencies.

Research suggests that interrupts are categorized into hardware and software
types. Hardware interrupts, triggered by external devices, are often
asynchronous to the processor's clock and include maskable interrupts (which
can be ignored if the processor is busy) and spurious interrupts (occurring
without a valid reason). Software interrupts, on the other hand, are generated
by the program itself, such as system calls (e.g., fork() as detailed at fork()
system call) or exceptions like division by zero.

The interrupt handling process involves several steps: the device raises an
interrupt request (IRQ), the processor finishes the current instruction, saves
its state (e.g., registers and program counter) on the stack, jumps to the
Interrupt Service Routine (ISR) at a predefined address (often via vectored
interrupts, where each device has a unique memory address for its ISR),
executes the ISR, and then restores the state to resume the original program.
This sequence is detailed in resources like Interrupts Overview, which
emphasizes the importance of timely responses in embedded systems.

32
Interrupt latency, the time between interrupt generation and ISR execution, is
a critical metric, especially for time-sensitive applications. Factors affecting
latency include the number of interrupts, enabled interrupts, handleable
interrupts, and the time taken to handle each. The evidence leans toward
minimizing latency to ensure responsiveness, with mechanisms like interrupt
nesting (prioritizing higher-priority interrupts) and priority schemes (e.g.,
fixed priority, dynamic priority, round-robin) playing key roles in managing
multiple interrupts, as discussed at Interrupts in computing.

How Do They Relate?

Timers often generate interrupts to handle time-sensitive tasks. For example,

a timer might interrupt every second to toggle an LED, allowing the
microcomputer to focus on other tasks while maintaining precise timing. This
synergy enhances responsiveness and efficiency.

Interrelationship Between Timing and Interrupts

The interplay between timing and interrupts is central to efficient

microcomputer operation, particularly in embedded systems. Timers often
generate interrupts to handle time-sensitive tasks, creating a synergy that
enhances responsiveness and efficiency. For instance, a timer can be set to
interrupt every second, triggering an ISR to toggle an LED, as demonstrated
in code examples for the ATmega2560 at Internal Timers and Interrupts. The
code sets OCR1A to 31250 for a 1-second interval at 16 MHz with a 256
prescaler, and the ISR toggles a port pin, ensuring precise timing without
continuous polling.

This approach is more efficient than polling, as it allows the processor to

handle other tasks while waiting for the timer event. In real-time systems,
such as control systems or data acquisition, this is crucial for maintaining
bounded, short latency, as noted in Chapter 12: Interrupts. The automatic
acknowledgment of SysTick interrupts, where no explicit software action is
needed to clear the trigger flag, further enhances efficiency.

Interrupt nesting and priority schemes, such as fixed priority (handling the
highest priority first) or round-robin for same-priority interrupts, ensure that
time-critical tasks are prioritized, as detailed at Interrupts. Triggering
methods, like level-trigger (signal held at active logic level) and edge-trigger
(triggered by rising/falling edge), also influence timing, with edge-trigger often

33
requiring additional hardware for detection, as discussed at Interrupts in
8086 microprocessor.

Practical Applications and Examples

Practical applications illustrate the integration of timing and interrupts. For

example, multiplexing 7-segment displays using interrupts in PIC
microcontrollers can lead to cumulative delays in timing applications, as noted
in Interrupts and timing applications. Solutions include using more efficient
segment driving routines or serial displays to mitigate delays, highlighting the
challenges of real-world timing with frequent ISRs.

Another example is error handling, where interrupts are used to detect and
recover from hardware or software errors, as mentioned at Interrupts in 8085
Microprocessor. This is particularly useful in input/output operations,
allowing the microprocessor to perform other tasks while waiting for data
transfer, enhancing system utilization.

Conclusion

Timing and interrupts in microcomputers are intricately linked, with timers

providing precise time measurement and interrupts ensuring responsive event
handling. Their integration is vital for real-time systems, enabling efficient
multitasking, accurate timing, and minimal latency. The complexity varies by
system, but the evidence strongly supports their role in enhancing
microcomputer performance, as seen in practical applications like LED
blinking and data acquisition.

PERIPHERAL INTERFACE CONNEECTOR

The Peripheral Interface Connector (often referred to in various contexts

such as PCI, USB, GPIO headers, etc.) is a general term that refers to
hardware interfaces used to connect peripheral devices (e.g., keyboard,
mouse, printer, external storage, etc.) to a central processing system like a
microcontroller, microprocessor, or computer.

Here's an overview of key types and aspects of Peripheral Interface

Connectors:

34
1. Types of Peripheral Interface Connectors

a. Parallel Peripheral Interfaces

GPIO (General Purpose Input/Output):

Simple digital I/O pins on microcontrollers.

Used for basic peripherals like LEDs, buttons, sensors.

Intel 8255 PPI (Programmable Peripheral Interface):

Common in older microprocessor systems (e.g., 8085/8086).

Has 3 8-bit ports: Port A, Port B, Port C.

Used for controlling/reading from devices like displays, switches, etc.

b. Serial Peripheral Interfaces

UART (Universal Asynchronous Receiver/Transmitter):

Used for asynchronous serial communication (e.g., RS-232).

Devices: GPS modules, GSM modules, etc.

SPI (Serial Peripheral Interface):

Full-duplex, high-speed, 4-wire interface (MISO, MOSI, SCLK, CS).

Used with SD cards, sensors, LCDs.

35
I2C (Inter-Integrated Circuit):

Two-wire (SDA, SCL) serial bus, supports multiple devices.

Widely used in sensors, RTCs, EEPROMs.

USB (Universal Serial Bus):

Standard interface for external peripherals.

Supports hot-plugging, power delivery, and high data rates.

PCI/PCIe (Peripheral Component Interconnect Express):

High-speed internal interface for graphics cards, SSDs, network cards.

PCIe is the modern version with lanes for faster data transfer.

---

2. Functions

Provide electrical and mechanical connections between devices and processor.

Allow communication through data, address, and control signals.

May supply power to peripherals (USB, GPIO, etc.).

---

3. Applications

Connecting input/output devices (keyboards, sensors, etc.).

Memory expansion (e.g., SD cards via SPI).

36
Networking (e.g., Ethernet modules via SPI or PCIe).

Multimedia (HDMI interfaces, audio codecs via I2S).

---

4. Design Considerations

Voltage levels (3.3V, 5V compatibility).

Data rate requirements.

Pin availability on the processor.

Power consumption and management.

Protocol support in firmware/software.

INSTRUCTION SETS

An instruction set is a collection of commands that a CPU (Central Processing

Unit) can understand and execute. It acts as the interface between software
and hardware, defining how a processor responds to binary commands.

Key Points:

Types of instructions: Include data movement (e.g., MOV), arithmetic/logic

operations (e.g., ADD, SUB), control flow (e.g., JMP, CALL), and
input/output operations.

Instruction Set Architecture (ISA): The design of the instruction set, including
the format and capabilities. Examples include x86, ARM, MIPS, and RISC-V.

CISC vs. RISC:

CISC (Complex Instruction Set Computing): Fewer lines of code but more
complex instructions (e.g., x86).

37
RISC (Reduced Instruction Set Computing): Simpler, faster instructions,
often requiring more lines of code (e.g., ARM).

TIMING AND INTERRUPTS

In microprocessors, timing and interrupts are crucial for efficient operation.

The Timing and Control Unit generates signals to synchronize operations,
while interrupts allow the processor to respond to external events and
prioritize tasks.

Timing:

·The Timing and Control Unit (TCU) generates clock signals and control
signals (like Read/Write)to orchestrate the microprocessor's activities.

·These signals ensure that operations occur in a precise sequence, allowing the
microprocessor to fetch instructions, execute them, and communicate with
memory and peripherals,

·The TCU ensures that all components of the system operate in a coordinated

Manner, preventing data races and other issues,

Interrupts:

Interrupts allow external devices or software to interrupt the

●」

Microprocessor’s current task and request its attention,

·Interrupts enable real-time processing, multi-tasking, and efficient handling

of input/output operations.

They allow the microprocessor to respond quickly to external events, like user
input or hardware signals, and prioritize tasks based on urgency.

Interrupts can be hardware-generated (e.g. From a peripheral device)or

Software-generated (e.g., through a software interrupt instruction).

38
Benefits of Timing and Interrupts:

·Real-time processing:

Interrupts enable the microprocessor to respond to external events in real-

time, which is crucial for applications like control Systems and data
acquisition.

·Multi-tasking:

Interrupts allow the microprocessor to switch between different tasks, making

it appear as if it is running multiple programs simultaneously.

·Efficiency:

Interrupts can optimize the use of processor time by allowing the

microprocessor to perform other tasks while waiting for external events or I/0
operations to complete.

·Flexibility:

Timers and interrupts provide a flexible way to manage the flow of control in
a system, allowing for responsive and adaptive behavior.

HIGH-LEVEL PROGRAM FOR MICRO PROCESSOR

WHAT IS HIGH-LEVEL PROGRAMMING?

High-level programming refers to writing source code using languages that

are closer to human language and further from machine language. These
languages support features like:

High-level programming abstracts the underlying hardware, allowing

developers to focus on functionality rather than intricate hardware details.
This shift enables faster development, easier debugging, and better
portability.

Variables and data types

39
Control structures (loops, conditionals)

Functions and modules

Libraries and APIs

Object-oriented or structured programming paradigms

In microprocessor applications, the most common high-level language is C,

due to its balance between hardware control and abstraction.

Why Use High-Level Programming with Microprocessors?

1. Ease of
Development

2. Portability

3. Maintainability

4. Integration with
Libraries

5. Safety and Error

Checking

High-Level Languages Commonly Used in Microprocessor Programming

1. C Language

40
2. C++

3. Python

4. Embedded Rust

Typical Applications of High-Level Programs in Microprocessors

1. Sensor Data
Acquisition and Processing

2. Communication
Interfaces

3. Real-Time
Control Systems

4. Graphical User
Interfaces (GUI)

5. Data Logging
and Storage

6. IoT Systems

Limitations and Considerations

Performance Overhead: High-level languages may produce less optimized

code than assembly.

Resource Constraints: Microprocessors with limited RAM and ROM may

require careful memory management.

Real-time Constraints: Ensuring deterministic behavior can be challenging

without real-time operating systems (RTOS).

41
To mitigate these issues, critical sections of code can be written in assembly or
optimized using compiler directives.

Conclusion

High-level programming has innovated the way developers interact with

microprocessors. It brings scalability, maintainability, and efficiency to
embedded systems development. As microprocessors become more powerful,
the role of high-level programming will continue to expand, empowering
engineers to build smarter, faster, and more reliable systems.

STRUCTURED PROGRAMMING, TEETABILITY AND

RECOVERABILITY

Structured programming is a programming paradigm(pattern) that facilitates

the creation of programs with readable code and reusable components. It is a
technique devised to improve the reliability and clarity of programs.
Structured programming encourages dividing an application program into a
hierarchy of modules or autonomous elements, which, in turn, may contain
other such elements. Within each element, code may be further structured
using blocks of related logic designed to improve readability and
maintainability. The languages that support structured programming are; C,
C++, Java, C# and Pascal, although the mechanisms of support vary. It may
be possible to build structured code using modules written in different
languages, as long as they can obey a common module interface or application
program interface specification.

Modules can be classified as procedures or functions:

A procedure is a unit of code that performs a specific task, usually referencing

a common data structure available to the program at large.

A function is a unit of code that operates on specific inputs and returns a

result when called. Some of the functions used in structured programming
are; IF THEN ELSE, DO WHILE, DO UNTIL, CASE.

Types of structured programming

There are three categories of structured programming:

42
Procedural programming. Defines modules as procedures or functions that
are called with a set of parameters to perform a task. A procedural language
begins a process, which is then given data. It is also the most common
category and is subdivided into the following:

Service-oriented programming simply defines reusable modules as services

with advertised interfaces.

Microservice programming focuses on creating modules that do not store data

internally and so are scalable and resilient in cloud deployment.

Functional programming, technically, means that modules are written from

functions, and that these functions' outputs are derived only from their inputs.
Designed for serverless computing, the definition of functional programming
has since expanded to be largely synonymous with microservices.

Object-oriented programming (OOP). Defines a program as a set of objects or

resources to which commands are sent. An object-oriented language defines a
data resource and sends it to process commands. For example, the procedural
programmer might say, "Print(object)," while the OOP programmer might
say, "Tell Object to Print."

Model-based programming. The most common example of this is database

query languages. In database programming, units of code are associated with
steps in database access and update or run when those steps occur. The
database and database access structure determine the structure of the code.
Another example of a model-based structure is Reverse Polish notation, a
math-problem structure that lends itself to efficient solving of complex
expressions. Quantum computing is another example of model-based
structured programming; the quantum computer demands a specific model to
organize steps, and the language simply provides it.

Advantages of Structured programming

Similar to English vocabulary of words and symbols.

It is easier to learn.

They require less time to write.

43
They are easier to maintain.

They are mainly problem oriented rather than machine based.

Program written in a higher-level language can be translated into many

machine languages and therefore can run on any computer for which there
exists an appropriate translator.

It is independent of machine on which it is used, i.e., programs developed in

high level.

It encourages top-down implementation, which improves both readability and

maintainability of code.

Disadvantages of Structured programming

Structured programming codes implemented in high-level language has to

be translated into the machine language by translator and thus a price in
computer time is paid.

The object code generated by a translator might be inefficient compared to

an equivalent assembly.

Reduction in execution efficiency and greater memory usage.

44