Rotary encoders from HEIDENHAIN are currently designed for the connection of KTY 84-130 temperature sensors. Future generations will be capable of processing other temperature sensor types (e.g., the PT 1000) in addition to the KTY 84-130.
However, the subsequent electronics or the rotary encoder installed in the motor can already now be configured to automatically detect the connected temperature sensor type. Information on the adaptations to the EnDat specification and recommendations for manufacturers of motors or subsequent electronics can be found in the EnDat Application Notes in the chapter “Processing of various temperature sensor types.” For more information on the compensation calculation by the subsequent electronics, please refer to the “Encoders for Servo Drives” brochure in the chapter “Temperature measurement in motors.”
For data storage, HEIDENHAIN encoders use so-called EEPROMs, which have a limited endurance due to their physical design. These encoders are thus of only limited suitability for the cyclical storage of data. For more information, refer to the EnDat Application Note.
The following RS-485 transceivers with fail-safe receivers are currently recommended by HEIDENHAIN, depending on the transmission frequency, temperature and supply voltage requirements. Identical blocks (same internal signal propagation time) must be used for clock and data: - THVD1450 (recommended for the common implementation of EnDat 2.2 and EnDat 3)- SN65HVD78 - MAX14841 - SN75HVD1176
These are the essential requirements on the RS-485 transceiver:
Application test under operating conditions: In all cases, an application test must be conducted, taking into account the complete transmission distance (RS-485 transceiver, cable, connector, etc.). This also applies to the application-specific requirements for the operating conditions, including voltage supply, temperature, EMC and ESD.
Before accessing the memory, the MRS code for the desired range must always be set first. An MRS range remains set until
a) a new MRS range is selectedb) an EnDat 2.1 reset is sentc) an EnDat 2.2 reset is sent
See also the EnDat Application Notes, Chapter “Sequences and data structures”
See also the “Sequences and data structures” chapter of the EnDat Application Note.
Error messages:The two composite error bits F1 and F2 should be monitored in every query. F1 and F2 are generated independently of each other, and must be evaluated separately from each other. It is recommended that errors and warnings be buffered in the subsequent electronics before they are cleared (for diagnostic purposes at a later date, e.g. error log). Clearing of errors and warnings is basically possible with EnDat 2.1 and EnDat 2.2 commands. However, not all causes of errors can be reset within one communication cycle with the EnDat 2.2 command. In these cases the error messages can remain set. The following priorities for the clearing of errors are the result (the timing requirements of an application decide when the next priority stage is to be switched to):
The group bit for warnings is transmitted with the additional data. The warning bit should be queried at regular intervals, even if the application does not require the processing of additional data.
Error handling of the interface:
Along with the CRC check there are three different types of errors, which should also be monitored continuously; see Attachment A2 of the EnDat specification.
Also see the “EnDat Monitoring Functions” section of the EnDat Application Note.
See also the EnDat Application Note, Chapter "Implementation Examples"
See also the EnDat Application Note, Chapter "EnDat Monitoring Functions"
Certain hardware and software combinations of the MASTERDRIVES inverters erroneously send a clock or entire clock-pulse group in the boot phase of the connected position measuring system. If the encoder is driven by a clock during the boot phase, this can lead to an interruption of the boot procedure and output of incorrect position values.
SIEMENS initiated a redesign of the MASTERDRIVES electronics (SBM 2) and developed appropriate software. These modifications will be available starting in December 2008. To ensure functional combinations of encoders and MASTERDRIVES for the transition period, HEIDENHAIN will modify, upon request, PCBs of the standard rotary encoders of the 35-mm and 56-mm series with optical scanning and deliver them in limited quantity. They can be distinguished by the index after the serial number according to the enclosure.
The following procedure is recommended to find out whether a combination of MASTERDRIVES and HEIDENHAIN encoder is functional:
Download Index list
(See also the EnDat Application Note, Chapter "OEM Memory Area".)
See also EnDat Technical Information
with incremental signals
without incremental signals
≤ 8MHz (bzw. 16 MHz)
bold: Standard version
The EnDat interface provides the possibility to reduce the recovery time for EnDat 2.2 mode commands (see EnDat specification). The reduction of the recovery time makes the realization of very short cycle times possible. The reduced recovery time led to misunderstandings regarding the specification data:
In the diagram in the EnDat specification it appears as if, after sending the mode word, I have to keep the clock at LOW, wait at least the time tCAL, and then the start bit appears immediately with the first clock pulse. I tried that with an encoder, and it worked. Is this correct, or do I continually have to send clock pulses and poll the start bit? A waiting period of 1 ms must be maintained when switching.
Unfortunately this is an incorrect interpretation of the diagram. It cannot be guaranteed that the behavior you described applies to all different encoder models. The dashed lines in the diagram indicate that the clock must continue to be sent to the encoder. The start bit must be polled; i.e. clock pulses must be sent until the start bit is sent. That is what the dashed lines in the diagram indicate. The EnDat 2.1 specifications and the EnDat 2.2 specifications refer to Appendix A4 and Appendix A5, respectively, several times. The timing for the EnDat 2.1 position command is described in Appendix A4/A5. Continued clocking while polling the start bit is described there. The time tCAL indicates the earliest possible time at which the position value can be retrieved from the encoder. The start bit must be polled independently of tCAL.
Due to the new scope of features of the EnDat02 interface, several encoder parameters differ from those of the predecessor encoders. For example, the measuring step was reduced from 100 nm to 5 nm, the OEM area was expanded, ….Because it is now possible to control the axis “purely serially” or “with sinusoidal signals,” the LC xx3 encoders have some special characteristics that must be noted for correct operation of the encoders.
EnDat 2.1 and 2.2 position requestsThe 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 the encoder specifications). 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 or EnDat 2.2 mode commands can be used for pure serial position-value transfer for axis control. Position requests with EnDat 2.1 take about 1 ms until the position values are available. For position requests with EnDat 2.2, the position values can be determined in about 5 µs. However, any active error message can then only be transmitted after a delay of approx. 1 ms, due to internal processing times. A one-time position request with EnDat 2.2 may not be performed.
Continuous clock (only possible with EnDat 2.1 position requests) Is not supported.
Clock interruptions A clock interruption during the LOW phase may not last longer than 30 ?s..
Interruption of an EnDat request The subsequent position request is not valid, and the encoder reacts with error type I or II.
Invalid memory access (incorrect MRS code)Interruption of an EnDat request Is at first acknowledged by the encoder with error type II. The subsequent position request transmits the last position value transmitted. No error message is output: EnDat 2.1 position request: One-time EnDat 2.2 position request: Up to 1 ms
Switching between EnDat 2.1 and EnDat 2.2 commands (either direction): A waiting period of 1 ms must be maintained when switching.
See also "Procedure After Switch-On" in the EnDat Application Note, Chapter 2 "Sequences and Data Structures"
Build-up time of supply voltage until Up.min is reached should be > 10 V/sec.
The 1 Vpp incremental signals attain valid values after at most 1.3 sec.
The encoder can be recognized as an EnDat or SSI encoder by the logic level on the data line, after power has been switched on.
Clock pulse edges during t1 or t2 can interrupt booting; this can only be corrected by switching the encoder off and then on again.
A first EnDat request (falling edge) is permissible once t3 has ended after at least 1 ms (there is no maximum time limit). After the first clock pulse, the direction of data on the data line is reversed (this is why the data line is then at “high impedance”).
The encoder requires a defined reset: Falling edge + end of recovery time; For the duration of the low phase the following applies: 0.125 < tlow < 30 µs
t1: Boot or reset time of the EnDat encoder
t2: Initialization phase of the EnDat encoder
t3: Must be maintained for downward compatibility to EnDat 2.1
The supported encoder types can be taken from the “parameters of the encoder manufacturer,” word 14:
The EnDat additional information must be processed for the connection of incremental encoders; For details, see the EnDat Application Note. The EnDat Master light cannot be used.
-> See the EnDat Application Note, Chapter 2:
“The additional data is saved in the non-volatile memory of the encoder, and not in the EEPROM. This is necessary to be able to switch between the pieces of additional data within a control cycle. Each additional data was assigned its own MRC code so that only one mode command is necessary for switchover. An address must not be specified. Not all encoders provide the full range of additional data. The available additional data can be read out of the EnDat 2.2 parameter, words 0 and 1.”/p>
As a rule, only supported additional data should be selected. If additional data that is not supported is selected, EnDat error type III is issued (see the EnDat Specification). In rare exceptions, a CRC error can be issued instead during the transmission of the corresponding additional data.
Error bits F1 and F2 play a central role here; see also the EnDat Application Note, Chapter 2, in the section on “General information on the processing of error messages, warnings and error handling in the interface.” This means that an error reaction should be triggered in reference to F1 or F2. Information contained in the error or warning register or in the operating status error sources is complementary information. For more information, see the EnDat Application Note, Chapter 7.
Simultaneous reading of the error or warning register through additional data 1 and of the operating status error sources through additional data 2 is not defined for the EnDat 2.2 interface, and can result in incorrect information.
These encoders differ from encoders with gear-based revolution counters in particular regarding how error messages are handled as well as the referencing of the multiturn range. For details, see the appropriate chapter of the EnDat Application Note.
Maximum 40-bit data width for the position value.
Maximum 48-bit data width for the position value.
It is recommended that the maximum possible data widths be available, so that future generations of encoders can also be connected. The trend is towards ever higher resolutions.
32-bit data width
Definitively not enough. For example, the EQN 1337 has 12-bit multiturn and 25-bit singleturn resolution, for a total of 37 bits of position information.