Technical Information

EnDat 2.2 Bidirectional Interface for Position Encoders

Digital drive systems and feedback loops with position encoders for measured value acquisition require fast data transfer with high transmission reliability from the encoders. Further data, such as drive-specic parameters, compensation tables, etc. must also be made available. For high system reliability, the encoders must be integrated in routines for error detection and have diagnostic capabilities. The EnDat interface from HEIDENHAIN is a digital, bidirectional interface for encoders. It is capable both of transmitting position values from incremental and absolute encoders as well as transmitting or updating information stored in the encoder, or saving new information. Thanks to the serial transmission method, only four signal lines are required. The data are transmitted in synchronism with the clock signal from the subsequent electronics. The type of transmission (position values, parameters, diagnostics, etc.) is selected by mode commands that the subsequent electronics send to the encoder.

Power supply 5 Vdc CLOCK 8 MHz

DATA Position values, parameters, datum shift,

electronic ID label, diagnostics, warning, ...

Benets of the EnDat Interface

The EnDat interface provides everything needed to reduce system costper axis up to 50%and at the same time improve the technical standard. The most signicant benets are:

Cost optimization: A single interface for all absolute and incremental encoders Simple subsequent electronics with EnDat receiver chip and standard components Simpler, more economical power supply, since remote sensing is not required Simple connection technology: Standard connecting elements (M12 8-pin), single shielded standard cable and low wiring costs Small motor or system dimensions through compact connecting elements No expensive additional sensory analysis and wiring: EnDat 2.2 transmits additional information (limit switch/ temperature/acceleration) Faster conguration during installation: Datum shifting through offsetting by a value in the encoder

Improved quality Higher system accuracy through specic optimization in the encoder High contour accuracy, particularly for CNC machine tools: position value formation in the encoder permits shorter sampling intervals without inuencing the computing time of the CNC Higher availability Automatic conguration of the system axis: all necessary information can be saved in the encoder (electronic ID label). High system reliability through purely digital data transmission Diagnosis through monitoring messages and warnings that can be evaluated in the subsequent electronics High transmission reliability through cyclic redundancy checking

Safety system (in preparation) EnDat 2.2 was conceived for safetyoriented machine designs Two independent error messages Two independent position information sources for error detection Checksums and acknowledgments Forced dynamic sampling of error messages and CRC formation by subsequent electronics Support for state-of-the-art machine designs Suitable for direct drive technology thanks to high resolution, short cycle times and commutation information Cyclic sampling every 25 s with full read and write mode Position values available in the subsequent electronics after only approx. 10 s

Simple connection technology, 8-wire cable, single shielding Miniature connecting element, M12, 8-pin

DATA DATA CLOCK CLOCK 5V UN 5 V *) UN *)

Simple subsequent electronics with EnDat 2.2 receiver chip and standard components

Connecting element, e.g. M12, D-sub

* For parallel power supply lines Power supply without remote sensing (5 V 5%)

Integrated interpolation and position value generation, temperature capture

Compatibility of EnDat 2.2 > 2.1

The extended EnDat interface version 2.2 is compatible in its communication, command set and time conditions with the previous version 2.1, but also offers signicant advantages. It makes it possible, for example, to transfer additional information with the position value without sending a separate request for it. The interface protocol was expanded and the time conditions were optimized as follows: Increased clock frequency (CLOCK) (8 MHz) Optimized calculating time (position value acquisition within 5 s) Minimized dead time (recovery time) (1.25 to 3.75 s) Expanded power supply range (3.6 V to 5.25 V at the encoder)

EnDat 2.2 command set (includes EnDat 2.1 command set) Position values for incremental and absolute encoders Additional information on position value Diagnostics, test values Absolute position values after reference run of incremental encoders Send and receive parameters Commutation Acceleration Limit position signal EnDat 2.1 command set Absolute position values Send and receive parameters Reset Test command Test values

Description of Function
The EnDat interface transmits position values or additional physical quantities in an unambiguous time sequence and serves to read out from and write to the encoder's internal memory. 1. Position values can be transmitted with or without additional information. The additional information types are selectable via the Memory Range Select (MRS) code. Other functions such as parameter reading and writing can also be called after the memory area has been selected. Through simultaneous transmission with the position value, additional information can also be requested of axes in the feedback loop, and functions executed with them. 2. Parameter reading and writing is possible both as a separate function and in connection with the position value. Parameters can be read or written after the memory area is selected. 3. Reset functions serve to reset the encoder in case of malfunction. Reset is possible instead of or during position value transmission. 4. Test commands and values are used for forced dynamization in safetyoriented controls. The signicance of the error message is inverted in order to monitor its generation. Moreover, for encoders with Gray-code scanning, the start-up diagnosticswhich tests the position value at standstillmust be started by a test command.

Data Transfer

A clock pulse (CLOCK) is transmitted by the subsequent electronics to synchronize data transmission. When not transmitting, the clock signal defaults to HIGH. Clock frequency and cable length Without propagation-delay compensation, the clock frequencydepending on the cable lengthis variable between 100 kHz and 2 MHz. Because large cable lengths and high clock frequencies increase the signal run time to the point that they can disturb the unambiguous assignment of data, the delay can be measured in a test run and then compensated. With this propagation-delay compensation in the subsequent electronics, clock frequencies up to 8 MHz at cable lengths up to a maximum of 100 m are possible. The maximum clock frequency is mainly determined by the cables and connecting elements used. To ensure proper function at clock frequencies above 2 MHz, use only original HEIDENHAIN cables. The permissible clock frequencies shown in the diagrams apply for a clock on-off ratio of 1:1. This means that the HIGH and LOW levels of the clock are equally long. For other on-off ratios, the theoretical clock frequency is calculated as fc = 1 2tmin Determining the propagation time After every change in the transmission line hardware, the propagation time must be ascertainedpreferably automatically after every power interruption. The subsequent electronics transmit the mode command Encoder transmit position values without additional information to the encoder. After the encoder has switched to transmission, i.e. after 10 clock periods in total, a counter in the subsequent electronics starts with every rising edge. The subsequent electronics measure the propagation time as the difference between the last rising

Clock frequency

Cable length [m]

0 300

1 000

2 000

4 000

6 000

8 000

Without delay compensation With delay compensation

Clock frequency [kHz]

Clock on-off ratio

t HI

t L0

Clock

clock pulse edge and the edge of the start bit. The process should run at least three times in order to rule out any disturbances during the calculation of the propagation time and to test the value for consistency. The signal propagation time is measured at a reduced clock frequency (100 kHz to

200 kHz). To attain sufcient accuracy, however, the value must be sampled at an internal frequency that is at least eight times higher than the clock frequency to be used later for data transmission.

Clock frequency 100 kHz to 200 kHz Clock pulse transmitted to the encoder Clock pulse at encoder Mode Data at encoder Data at subs. electronics Start counter
0 0 0 0 0 0 1 1 1 1 1 1 tD
S S F1 F1 D D D D D D D D CRC CRC CRC CRC CRC CRC CRC CRC CRC CRC

2T

Mode command

2T

S = start, F1 = error, D = data

Selecting the transmission type

Transmitted data are identied as either position values, position values with additional information, or parameters. The type of information to be transmitted is selected by mode commands. Mode commands dene the content of the transmitted information. Every mode command consists of three bits. To ensure reliable transmission, every bit is transmitted redundantly (inverted or double). If the encoder detects an erroneous mode transmission, it transmits an error message. The EnDat 2.2 interface can also transfer parameter values in the additional information together with the position value. This makes the current position values constantly available for the control loop, even during a parameter request.

The time absolute linear encoders need for calculating the position values tcal differs depending on whether EnDat 2.1 or EnDat 2.2 mode commands are transmitted (see Specications in the Linear Encoders for Numerically Controlled Machine Tools brochure). If the incremental signals are evaluated for axis control, then the EnDat 2.1 mode commands should be used. Only in this manner can an active error message be transmitted synchronously with the currently requested position value. EnDat 2.1 mode commands should not be used for purely serial position-value transfer for axis control.

Mode bit No. Mode command 1 2 3 4 5 6 7 8 Encoder transmit position values Selection of the memory area Encoder receive parameters Encoder transmit parameters Encoder receive reset1) Encoder transmit test values Encoder receive test commands Encoder transmit position value with additional information Encoder transmit position value and receive selection of memory area2) Encoder transmit position value and receive parameters2) Encoder transmit position value and transmit parameters2) Encoder transmit position value and 2) receive error reset Encoder transmit position value and receive test command2) Encoder receive communication command3)
1) 2)

M2 0

M1 0 0 1 0 0 1 1 1

M0 (M2) (M1) (M0) 0 1 1 0 1 0 0 1 1 1 1 0 0 1 0 0 1 1 0 1 1 0 0 0 1 0 0 1 0 1 1 0

EnDat 2.1 command set

0 0 1 1 0

EnDat 2.2 command set

1 1

10

11

12

13

14

Same reaction as switching the power supply off and on Selected additional information is also transmitted 3) Reserved for encoders that do not support the safety system

Position Values

One data packet is sent in synchronism per data transmission. The transmission cycle begins with the rst falling clock edge. The measured values are saved and the position value calculated. After two clock pulses (2T), the subsequent electronics transmits the mode command Encoder transmit position value (with/ without additional information). After successful calculation of the absolute position value (tcalsee table), the start bit begins the data transmission from the encoder to the subsequent electronics. The subsequent error bits, error 1 and error 2 (only with EnDat 2.2 commands), are group signals for all monitored functions and serve for failure monitoring. They are generated separately from each other and indicate when a malfunction of the encoder can result in incorrect position values. The exact cause of the disturbance is saved in the operating status memory and can be interrogated in detail. The encoder then transmits the absolute position value, beginning with the LSB. Its length varies depending on which encoder is being used. The number of required clock pulses for transmission of a position value is saved in the parameters of the encoder manufacturer. The data transmission of the position value is completed with the Cyclic Redundancy Check (CRC). This is followed in EnDat 2.2 by the additional information 1 and 2, each also concluded with a CRC. The content of the additional information is determined by the selection of the memory area and is transmitted in the next sampling cycle for additional information. This information is then transmitted with every sampling until a selection of a new memory area changes the content. With the end of the data word, the clock must be set to HIGH. After 10 to 30 s or 1.25 to 3.75 s (with EnDat 2.2 parameterizable recovery time tm) the data line falls back to LOW. Then a new data transmission can begin by starting the clock.

Position value package without additional information

Encoder saves position value Subsequent electronics transmit mode command
tcal tST
S F1 F2 L M

tm

tR

Mode command

Position value

CRC

S = start, F1 = error 1, F2 = error 2, L = LSB, M = MSB Diagram does not depict the propagation-delay compensation

Without delay compensation With delay compensation Clock frequency Calculation time for Position value Parameters Recovery time fc 100 kHz ... 2 MHz 100 kHz ... 8 MHz

tcal tac tm

Typical of EnDat 2.2 encoders: 5 s Max. 12 ms EnDat 2.1: 10 to 30 s EnDat 2.2: 10 to 30 s or 1.25 to 3.75 s (fc 1 MHz) (parameterizable) Max. 500 ns 2 to 10 s

tR tST Data delay time Pulse width tD tHI

(0.2 + 0.01 x cable length in m) s 0.2 to 10 s Pulse width uctuation HIGH to LOW max. 10%

tLO 0.2 to 50 ms to 30 s (with LC)

Data packet with position value and additional information 1 and 2

Encoder saves position value Subsequent electronics transmit mode command
tcal tST
S F1 F2 L M

tm

tR

Mode command

Position value

CRC

Additional information 2

CRC

Additional information 1

CRC

S = start, F1 = error 1, F2 = error 2, L = LSB, M = MSB

Diagram does not depict the propagation-delay compensation Typical command sequence when transmitting a position value with additional information:
Subsequent electronics transmit Encoder transmit position value and receive selection of memory area (selection of the desired additional information) Encoder transmit position value and receive selection of memory area (acknowledgment of the MRS code) Mode command 001 001 Encoder transmits Position value Position value Subsequent electronics transmit MRS Random content

Mode command 001 001

01000111 Random Acknowledgcontent ment request for MRS code

Encoder transmit position value with additional information (acknowledgment)

Mode command 111 000

Position value

Additional info 1 MRS acknowledgment

Content of the data packet Error messages 1 and 2 The EnDat interface enables comprehensive monitoring of the encoder without requiring an additional transmission line. An error message becomes active if a malfunction of the encoder might result in incorrect position values. At the same time, the cause of error is saved in the encoder. Errors include, for example, Light unit failure Signal amplitude too low Error in calculation of position value Power supply too high/low Current consumption is excessive For reasons of security it is necessary to generate a second, independently acquired error message. This is transmitted with inverted level as error message 2. Position value The position value is transmitted as a complete data word whose length depends on the resolution of the encoder. Transmission begins with the LSB (LSB rst). Additional information One or two additional data can be appended to the position value, depending on the type of transmission (selection via MRS code). The additional data are each 30 bits in length, with LOW as rst bit. Each additional data is concluded with a CRC that is formed from the respective additional information without the rst bit or the CRC.

The additional information supported by the respective encoder is saved in the encoder parameters. The additional information includes status information, addresses, and data.

30 bits Additional information

5 bits CRC

WRN

RM Busy

Information (content) 8 bits for address or data + 8 bits for data

Status data WRNWarnings This collective bit indicates whether certain tolerance limits of the encoder have been reached or exceeded, for example rotational speed or light source control reserve, without necessarily indicating an incorrect position value. This function makes it possible to issue preventive warnings in order to minimize idle time. The cause of the warning is stored in the encoder memory. The alarms and warnings supported by the respective encoder are saved in the "parameters of the encoder manufacturer" memory area. RMReference marks The RM bit indicates whether the reference run has been completed. In incremental systems, this is required in order to establish the absolute reference to the machine reference system. The absolute position value can then be read from the additional information 1. On absolute encoders the RM bit is always on HIGH. Busyparameter request When LOW, the busy bit indicates that a parameter request (read/write) is possible. If a request is being processed (HIGH), the encoder memory cannot be accessed.

Content of the additional information The content of the additional information is dened by the mode command for selection of a memory area. This content, updated with each clock pulse, is transmitted until there is a new request. The following contents are possible: Additional information 1 Diagnosis Cyclic information on encoder function and additional diagnostic values. Position value For incremental encoders: Relative position information (counter starts from zero at switch-on). The absolute position value is only available after the reference marks have been traversed (RM bit HIGH). For absolute encoders: Second absolute position value. Memory parameters Parameters saved in the encoder can also be transmitted along with the position values. The request is dened via memory range selection, followed by output of the parameters with the associated address. MRS-code acknowledgment Acknowledgment of the requested memory area selection

Test values Test values serve for inspection purposes, in service diagnostics, for example. Temperature Transmission of temperature in encoders with integrated evaluation of temperature sensors. Additional sensors The EnDat 2.2 protocol enables the connection of 16 additional sensors (4-bit address). The sensor values increase by x+1 for each request. The associated sensor is identied by the address supplied. Additional information 2 Commutation Some incremental encoders provide rough position information for commutation in electric motors. Acceleration If the encoder has additional sensor systems for acceleration, it can transmit the results. Limit position signals Limit position signals and homing information. Asynchronous position value Position formed by oversampling between two "regular" requests. Operating status error sources, operating status warning sources Detailed information about the cause of the present error message or warning.

MRS code for selection of additional information

Additional information 1 C7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 . . 0 C6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 . . 1 C5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 . . 0 C4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 . . 1 C3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 . . 1 C2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 . . 1 C1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 . . 1 C0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 . . 1 Transmit additional information 1 without data content (NOP) Transmit diagnosis Transmit position values 2 word 1 LSB Transmit position values 2 word 2 Transmit position values 2 word 3 MSB Acknowledge memory content LSB Acknowledge memory content MSB Acknowledge MRS code Acknowledge test command Transmit test values word 1 LSB Transmit test values word 2 Transmit test values word 3 MSB Transmit temperature 1 Transmit temperature 2 Additional sensors Transmit no more additional information 1 Transmit additional information 2 without data content (NOP) Transmit commutation Transmit acceleration Transmit commutation and acceleration Transmit limit position signal Transmit limit position signal and acceleration Asynchronous position value word 1 LSB Asynchronous position value word 2 Asynchronous position value word 3 MSB Operating status error sources Operating status warning sources (Not used at present) Transmit no more additional information 2

Additional information 2

Parameters Memory areas

The encoder provides several memory areas for parameters. These can be read from by the subsequent electronics, and some can be written to by the encoder manufacturer, the OEM, or even the end user. Certain memory areas can be writeprotected. The parameters, which in most cases are set by the OEM, largely dene the function of the encoder and the EnDat interface. When the encoder is exchanged, it is therefore essential that its parameter settings are correct. Attempts to congure machines without including OEM data can result in malfunctions. If there is any doubt as to the correct parameter settings, the OEM should be consulted.
Operating parameters Operating status

Absolute Encoder

Subsequent electronics
1 VPP A*) 1 VPP B*) EnDat interface *) Depends on encoder

Incremental signals *)

Absolute position value

Parameters Parameters of the encoder of the OEM manufacturer for EnDat 2.1 EnDat 2.2

Block diagram of absolute encoder with EnDat Interface

Parameters of the encoder manufacturer This write-protected memory area contains all information specic to the encoder, such as encoder type (linear, angular, singleturn/multiturn, etc.), signal periods, number of position values per revolution, transmission format of absolute position values, direction of rotation, maximum permissible speed, accuracy dependent on shaft speeds, support from warnings and alarms, part number, and serial number. This information forms the basis for automatic conguration. A separate memory area contains the parameters typical for EnDat 2.2: Status of additional information, temperature, acceleration, support of diagnostic and error messages, etc.

Parameters of the OEM In this freely denable memory area, the OEM can store his information, e.g. the electronic ID label of the motor in which the encoder is integrated, indicating the motor model, maximum current rating, etc. Operating parameters This area is available to the customer for a datum shift and the conguration of diagnostics. It can be protected against overwriting. Operating status This memory area provides detailed alarms or warnings for diagnostic purposes. Here it is also possible to activate write protection for the OEM parameter and operating parameter memory areas, and to interrogate their status. Once activated, the write protection cannot be reversed.

Parameters of the encoder manufacturer

The meaning of the information contained in the parameters of the encoder manufacturer depends on the encoder. HEIDENHAIN encoders can be divided into six groups. They are differentiated by the type of encoder (word 14 of the EnDat 2.1 parameters). Encoder types: L Linear encoders W Angle encoders (rotational) D Rotary encoders (rotational) E EIB external interface box for conversion of 1 VPP to pure serial EnDat 2.2 iL Incremental linear encoder with integral conversion of 1 VPP to pure serial EnDat 2.2 iR Incremental rotational encoder with integral conversion of 1 VPP to pure serial EnDat 2.2

The meanings of parameters are divided into evaluation categories. On the basis of these categories, the user can make clear decisions on the use of parameters and their integration in the application software. Evaluation categories: Required: It is essential for operation that these parameters be considered. Depends on application: Whether these parameters are to be considered depends on the customer's application. If, for example, no OEM range is used, then the parameter regarding memory allocation for parameters of the OEM need not be considered. Informative: These parameters are not required for encoder operation, but they give the user additional information such as the model number. Not relevant: If no encoder types were assigned to any of the three other evaluation categories, then the parameter is not required for encoder operation and can be ignored.

The additional information for EnDat 2.2 contained in the parameters of the encoder manufacturer depends in part on the respective encoder. EnDat 2.2 parameters can be read out only with EnDat 2.2 mode commands. The types of additional information, additional functions, diagnostic values, and specications that the respective encoder supports are saved in the assigned status words of these memory areas. Before interrogation of the additional information, HEIDENHAIN recommends reading out the supported information and functions (typically for every initialization of encoders). They are also shown in the encoders' specications.

Parameters of the encoder manufacturer for EnDat 2.1

Depends on application Required Word Content Linear encoder Rotary/angle encoder Informative Unit for Remark

4 5 6 7 8 9 10 11 12 13 14 15 16

Mask 0 Mask 1 Mask 2 Mask 3 Version of the EnDat Interface Memory allocation for parameters of the OEM Memory allocation for compensation values Number of pulses for transfer of position value (transmission format) Encoder type Signal period or signal periods per revolution for incremental output signals Distinguishable revolutions (only for multiturn encoders) (Nominal) increment of reference marks Position of rst reference mark

nm

All

All

2 saved with EnDat 2.1 or 2.2 Depends on encoder; program exibly. Memory pointer to rst free address Reserved for encoder manufacturer Setting the correct clock number for position transmission Denes the units of the parameters E, iL, iR: for calculating the smallest display step (LSB) or the correct display value for negative traverse direction All: for EnDat-compliant datum shift Required for correct calculation of the position. Not supported by EIB.

All All All

17 18 19

mm mm

Signal periods

WD

E iL iR iL

10

Parameters of the encoder manufacturer for EnDat 2.1 (continued)

Depends on application Required Word Content Linear encoder Rotary/angle encoder Informative Unit for Remark

20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Measuring step or steps per revolution nm with serial data transmission Datum shift of the encoder manufacturer ID number Signal periods

Measuring steps per revolution Signal periods

All

All

All

To be accounted for by the user for datum shift Safety technology

Serial number

All

Encoder exchange can be detected (may affect applicationsafety related)

Direction of rotation or traverse Status of commissioning diagnosis Maximum mechanically permissible linear velocity or shaft speed Accuracy depending on linear velocity or shaft speed, Area I Accuracy depending on linear velocity or shaft speed, Area II Support of error messages 1 Support of warnings EnDat command set Reserved for measuring length 2) Maximum calculating time HEIDENHAIN specications

m/min LSB 1) LSB 1)

rpm LSB 1) LSB 1)

All All All All

WLD iL iR WLD WLD

All L iL

No longer supported since 1999 Required for cross checking of absolute position incremental position Comparison of absolute and incremental position not possible with E iL iR, because these encoders have only incremental information For denition of an error mask (safety related) For preventive maintenance Information whether EnDat 2.2 mode commands are supported Not supported by EIB. For monitoring (time out)

CHECKSUM
1)

The higher-valued byte contains the divisor with respect to the maximum permissible linear velocity or rotational shaft speed up to which this accuracy is valid. 2) Not supported by all linear encoder models; initialized with default value 0.

11

Parameters of the encoder manufacturer for EnDat 2.2

Unit for Depends on application Informative Word Content Required Linear encoder Rotary/ angle encoder Remark

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 to 20 21 22 23 24 25 26 27 28 29 30

Status of additional information 1 Status of additional information 2 Status of additional functions Acceleration Temperature Diagnostic status Support of error message 2 Forced speed-up status Measuring step or measuring steps per revolution for position value 2

m/s2 K nm

1/s2 K LSB1) LSB1) LSB 1) LSB 1)

All

All All All All All All

All

Can be safety related. Cross checking of what is required and what does the encoder support Consider the scaling factor. Consider the scaling factor. For denition of an error mask: (safety related) Safety technology Safety technology or EIB, iL, iR Safety technology or EIB, iL, iR Safety technology or EIB, iL, iR Safety technology or EIB, iL, iR Safety technology or EIB, iL, iR Required for correct calculation of the position

All WD All All All All All All

Accuracy depending on linear velocity or LSB1) shaft speed of position value 2, Area I LSB1) Accuracy depending on linear velocity or LSB 1) shaft speed of position value 2, Area II LSB 1) Distinguishable revolutions Position value 2 (only for multiturn encoders) Encoder designation

Direction of rotation of position value 2

Support of instructions

K 1/s2 kHz

All All All All

WLD iL iR WLD iL iR All

Not yet supported. Not for safety technology Not supported by EIB. Not supported by EIB. Depends on encoder; program exibly Depends on connector, cable lengths Safety technology For calculation of the smallest display step (LSB).

Max. permissible encoder temperature K at measuring point Max. permissible acceleration Number of blocks for memory area Section 2 Maximum clock frequency Scaling factor for resolution Measuring step or measuring steps per revolution or subdivision values of a grating period Max. velocity or shaft speed for continuous code value Offset between position value and position value 2 m/s2 kHz

Number of bits for position comparison

m/min

rpm

WLD iL iR All

Specic to application. Applies for encoders that permit higher mechanical than electrical speed. Not supported by the EIB Safety technology

31 32 33 34 63

Number of distinguishable revolutions with scaling factor CHECKSUM

1)

WD

Required for correct calculation of the position

The higher-valued byte contains the divisor with respect to the maximum permissible linear velocity or rotational shaft speed up to which this accuracy is valid.

12

Transmission of parameters

Control cycles for transfer of parameters (EnDat 2.1 mode command 001110) Before parameter transfer, the memory area is specied with the selection of memory area mode command. The possible memory areas are stored in the parameters of the encoder manufacturer. Due to internal access times to the individual memory areas, the time tac may reach 12 ms.

Reading parameters from the encoder (EnDat 2.1 mode command 100011) After selecting the memory area, the subsequent electronics transmit a complete communications protocol beginning with the mode command Encoder transmit parameters, followed by an 8-bit address and 16 bits with random content. The encoder answers with the repetition of the address and 16 bits with the contents of the parameter. The transmission cycle is concluded with a CRC check.

Writing parameters to the encoder (EnDat 2.1 mode command 011100) After selecting the memory area, the subsequent electronics transmit a complete communications protocol beginning with the mode command Encoder receive parameters, followed by an 8-bit address and a 16-bit parameter value. The encoder answers by repeating the address and the contents of the parameter. The CRC check concludes the cycle.

tac

Transmitter in encoder inactive Receiver in encoder active

Transmitter in encoder active

8 bits

16 bits

8 bits

16 bits

MRS code Address Address x = random y = parameter

MRS code Address Address Acknowledgment Parameter

Typical EnDat 2.2 command sequence for transmitting a position value with parameter values in the additional information (max. 12 ms access time by interrogating the integrated EEPROM)
Subsequent electronics transmit Encoder transmit position value and receive selection of memory area (selection of the desired additional information) Encoder transmit position value and receive selection of memory area (acknowledgment of the MRS code) Mode command 001 001 Encoder transmits Position value Subsequent electronics transmit MRS Random content

Mode command 001 001

Position value

01000111 Acknowledgment request for MRS code

Random content

Encoder transmit position value with additional information (acknowledgment)

Mode command 111 000

Position value

Additional info 1 MRS acknowledgment

Encoder transmit position value and transmit parameters Encoder transmit position value with additional information

Mode command 100 100 Mode command 111 000

Position value

Address

Random content

Position value

Additional info 1 Busy = 1/no data

Parameter value is not yet available, therefore the busy bit is at 1. Encoder transmit position value with additional information Encoder transmit position value with additional information Max. 12 ms Encoder transmit position value with additional information Mode command 111 000 Position value Additional info 1 Busy = 0/parameter Mode command 111 000 Mode command 111 000 Position value Additional info 1 Busy = 1/no data Additional info 1 Busy = 1/no data

Position value

This concludes the request. A new parameter value can be requested from a new address.

13

Diagnosis

The EnDat interface makes extensive monitoring and diagnosis of an encoder possible without an additional line. The diagnostic system generates error messages and warnings (see Position values), and is a signicant prerequisite for the high level of availability of the complete system. Online diagnostics are growing in signicance. Decisive points of emphasis are: Machine usage planning Support for the service technician on-site Simple evaluation of encoder function reserves Simplication of trouble-shooting for repair Generation of meaningful quality statistics On encoders with incremental signals, EnDat makes it possible to use Lissajous gures to analyze signal errors and what they mean for encoder function. Encoders with pure serial interfaces to not provide incremental signals. Encoders with EnDat 2.2 can cyclically output the evaluation numbers in order to evaluated the functions of the encoder. The evaluation numbers provide the current state of the encoder and ascertain the encoder's functional reserves. Their scaling is identical for all HEIDENHAIN encoders. This makes integrated evaluation possible. The evaluation numbers supported by the respective encoder is saved in the EnDat 2.2 parameters. Composition and interrogation of the transmitted diagnostics data: The desired evaluation numbers must be activated. The value (8 bits) is transmitted over the additional information 1. The values are output in a cyclic process; address and value. The information as to which evaluation numbers are supported is saved in the EnDat 2.2 parameters. The diagnostics information can be transmitted in the closed loop mode. The border areas should be suppressed in the display (denition of reserve areas is required). Unknown addresses (system data) must be ignored in the subsequent electronics.
WRN RM Busy

30 bits Additional information

5 bits CRC

Information (content) 8 bits for address + 8 bits for data

The evaluation numbers in EnDat 2.2 are provided in the additional information.

Screen showing the evaluation numbers as functional reserves (e.g. with IK 215)

Activation of diagnosis

Interrogation of diagnostics data Encoder transmit position value with additional information

Adaptation of synchronism to a valid packet header. (non-supported addresses system data must be suppressed)

Determination and display of valid evaluation numbers

Flow chart for interrogation of diagnostics data

14

Conguration

Function initialization In word 3 of the operating status, the customer can dene the functions of data transmission or special function modes of the encoder. In the default setting, all additional information data are deactivated and the recovery time is programmed at 10 s tm 30 s. Recovery time can be changed to 1.25 s tm 3.75 s only for the EnDat 2.2 command set. For clock pulse frequencies 1 MHz, recovery time must remain set to 10 s tm 30 s. The oversampling and EnDat-2.2 commands are reserved for future applications, and cannot yet be activated. In the future, the multiturn functions will enable connection of battery-buffered encoders.

Information Recovery time tm

Condition upon delivery 10 s tm 30 s Adjustable to 1.25 s tm 3.75 s1) Deactivated Deactivated Activated Deactivated Deactivated Deactivated Deactivated

Reference pulse initialization Oversampling EnDat 2.2 commands Multiturn overow alarm Multiturn overow latch Multiturn position alarm Multiturn counter reset
1)

Valid only for the mode commands 8 to 14 of the EnDat 2.2 command set

Conguration of Diagnosis In word 3 of the operating status, the customer can dene the conguration of the diagnosis for the Encoder transmit position values with additional information mode command. In the factory default setting, all available evaluation numbers are activated, and this setting should normally not be changed. They provide the maximum depth of information on the encoder's function reserves. Valuation number 1 Valuation number 2 Valuation number 3 Valuation number 4 System-specic data

=0 Deactivated Deactivated Deactivated Deactivated Deactivated

=1 Activated Activated Activated Activated Activated

The conguration is not activated until the encoder receive reset mode command has been transmitted.

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Interface Power supply and switch-on

Power supply The encoders require a stabilized dc voltage. Voltage between 4.75 and 5.25 V must be available at the supply point (subsequent electronics). The encoders are designed so that the resulting voltage after attenuation through cable length, cable cross section and current consumption can be processed without correction (applies only for cable assemblies from HEIDENHAIN). The permissible ripple content of the dc voltage is: High frequency interference UPP < 250 mV with dU/dt > 5 V/s Low frequency fundamental ripple UPP < 100 mV Starting behavior at the encoder The integrated electronics require an initialization time of approx. 1 s, whereby the initialization phase should be taken into account (see Clock pulse sequence from the subsequent electronics at right).

Power supply from subsequent UP limit electronics UP max. (supply point) UP min. see the Specications of the encoder
Supply voltage

Start UP rated

800 ms t1 any 80 ms t2 120 ms 380 ms t3 420 ms

0V

Reaction of the encoder

Encoder data
t1 t2 t3

*)

Clock pulse sequence from the subsequent electronics

Max. 50 ms Clock Valid HIGH or LOW level undened

Min. 1 ms

At least one pulse (>125 ns) or one request cycle (data not valid) *) high-impedance

After conclusion of the initialization phase, a certain switch-on routine is necessary. Only EnDat 2.1 mode commands can be used for this purpose.

Encoder's initialization phase is concluded

Encoder reset Encoder receive reset mode command

Wait for 50 ms

Read out and buffering of alarms and warnings

Deletion of alarms

Deletion of warnings

Readout of Number of pulses for transfer of position value. (Parameters of the encoder manufacturer, word 13)

Inquiry whether the encoder supports EnDat2.2 commands. (Parameters of the encoder manufacturer, word 37)

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Input circuitry of the subsequent electronics

Data (measured values or parameters) can be transferred bidirectionally between position encoders and subsequent electronics with transceiver components in accordance with RS-485 (differential signals), in synchronism with the clock signal produced by the subsequent electronics. Dimensioning IC1 = RS 485 differential line receiver and driver C3 = 330 pF Z0 = 120

Data transfer

Encoder

Subsequent electronics

Incremental signals Depends on encoder

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Safety System

Safety-oriented controls are the planned application for encoders with EnDat 2.2 interface. The ISO 13 849-1 (previously EN 954-1) and IEC 61 508 standards serve as the foundation for this. These standards describe the assessment of safety-related systems, for example on the basis of failure probabilities of integrated components and subsystems. This modular approach helps manufacturers of safety-related systems to implement their systems, because they can begin with prequalied subsystems. Safety-related position encoders with pure serial data transmission via EnDat 2.2 accommodate this technique.

In a safe drive, the safety-related position measuring systemconsisting of encoder, data transmission line and EnDat 2.2 receiver component (master) with monitoring functionspresents such a subsystem. The safety-oriented control and the power stage with cable and drive complete the safe drive to form an entire system. The position measuring system is integrated over two interfaces into the complete system. The mechanical coupling of the encoder on the drive is determined by the encoder's geometry. Including the EnDat master into the safe control ensures its electrical integration. Certain measures are to be taken for the integration and evaluation of the EnDat master in the control in order to be able to use the safety system of the position encoder. With regard to a safe complete system, the remaining components are also to be approved by the auditing agency. Safety-related position measuring systems that are built into the feedback loop of the machine can be used as single-encoder systems in applications with control category SIL -2 (in accordance with IEC 61 508). This corresponds to performance level d of the EN 13 849 or category 3 according to the previous EN 954-1. Also, the functions of the safety-related position measuring

system can be used for the following safety functions in the complete system: Safe standstill Safe stop Safe operational stop Safe linear or rotational speed reduction Safe limited step Safe limited absolute position Safe limit of torque / power

Scanning in the encoders produces two independent position values that are transmitted over the EnDat 2.2 protocol to the EnDat master. The EnDat master provides the two position values and independent error bits to the safe control over two physically separated interfaces. A package of measures for the control describes the integration of the EnDat master into the control and the additional tasks of the control. The architecture of the position measuring system according to IEC 61 508 is regarded as a single-channel tested system. The testing consists of monitoring and comparison.

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The EnDat 2.2 interface supports the following individual safety-relevant functions: Two mutually independent position values for error detection In addition to the position value, the additional information includes a separately evaluated position value to be used for comparison in the subsequent electronics. Two mutually independent error messages The error messages are generated independently of each other and are transmitted at different active levels. Inversion or repetition of the mode commands The mode commands consist of 3 bits that are transmitted redundantly either inverted or repeated. The consistency is monitored in the encoder and acknowledged with an error response.

Independent individual CRC generation for position values and additional information Separate CRC values are generated for the individual data packets of a transmission (position value, additional information 1 and 2). Highly dynamic data acquisition and transmission Short cycle times for data acquisition including transmission make the necessary comparisons and monitoring of transmission functions possible. The safety-oriented control must support the corresponding communication with the master over two separate interfaces (interfaces 1 and 2). Furthermore, it must handle additional tasks, e.g.: Forced dynamic sampling of error messages Through the mode commands for requesting test values, the value of the error messages is inverted in order to monitor their generation.

Force dynamic sampling of the CRC monitoring in the subsequent electronics The CRC generation in the receiver chip (EnDat master) of the subsequent electronics must be ensured through a targeted execution of bit sequences with known result. Multiple transmission of position value during start-up To avoid errors during initialization, the position value must be transmitted repeatedly during start-up and compared. Following error monitoring in the subsequent electronics As a general additional check of the moving axes, the servo lag must be monitored in the subsequent electronics. Assume safe status in case of error

Encoder

Connecting cable

Subsequent electronics

EnDat slave Measured value acquisition (opto ASIC) Position value calculation (two position values through separate evaluation)

Data transmission line Serial data transfer EnDat 2.2 communications protocol

EnDat master in the subsequent electronics Organization of data transmission Position values 1 and 2 Evaluation of warning and error messages Forced dynamic sampling

Interface 1

Further processing of position values and messages

Interface 2

Safety-related position measuring system

User interface with package of measures

Safe control

In addition to the actual encoder, safety-related position measuring systems from HEIDENHAIN also include the transmission line and the EnDat master in the subsequent electronics.

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Overview of Encoders

EnDat is available in two versions, EnDat 2.1 and EnDat 2.2. Only EnDat 2.2 devices support functions such as short recovery time and additional information.

Absolute Encoders Linear encoders LC 183/LC 483 5 m 3 m

Resolution 0.01 m 0.005 m 26 bits 28 bits 29 bits

Angle encoders

RCN 226 RCN 228 RCN 729/RCN 829 Optical, singleturn ROC/ECN 425, ECN 1325, ECN 125 ROC/ECN 10xx/11xx Optical, multiturn ROQ/EQN 437 , EQN 1337 , ROQ/EQN 10xx/11xx Inductive, singleturn ECI 13xx ECI 11xx Inductive, multiturn EQI 13xx EQI 11xx

Rotary encoders

25 bits 24 bits1) 37 bits 36 bits1) 19 bits 18 bits1) 31 bits 30 bits1) Resolution Integrated 14-bit interpolation

Incremental Encoders Encoders with 1-VPP output signals over EIB (Externe Interface Box)
1)

Scheduled availability: 2007

DR. JOHANNES HEIDENHAIN GmbH Dr.-Johannes-Heidenhain-Strae 5 83301 Traunreut, Germany { +49 (86 69) 31-0 | +49 (86 69) 50 61 E-Mail: info@heidenhain.de www.heidenhain.de

For more information: HEIDENHAIN encoder brochures Description of the master component (in preparation) Detailed interface specication (upon request)

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383 942-23 15 7/2006 F&W Printed in Germany Subject to change without notice