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BiSS-C

BiSS-C is a digital encoder protocol that permits a wide range of possible formats. The AKD supports the most common BiSS-C format, and can only guarantee support for the encoders listed in "Documented BiSS-C Encoders". To determine if a BiSS-C device not listed here is supported by the AKD, follow the steps in "Setting Up an Undocumented BiSS-C Encoder"

Documented BiSS-C Encoders

The following BiSS-C encoders are known to work with an AKD. This list does not include BiSS-B encoders, which function differently.

Encoder Name BISSBITS Sine Cycles per Rev or Pole Pitch (FB1.ENCRES)
LMA10-xx-xxB-xx-x-03 LMA10 Magnetic Encoder, option 03, from RLS 26 (pole pitch / encoder bit resolution) * 64
S-9SRH-0398 Renishaw Rotary Encoder 32 4294967295
RL 26B / RL 32B / RL 36B Renishaw RESOLUTE Linear Encoder 26/32/36 (pole pitch / encoder resolution) * 2^(32-BISSBITS)
RA 18B / RA 26B / RA 32B Renishaw RESOLUTE Rotary Encoder 18/26/32 4294967295
AD36-0019 / AD58-0022 HENGSTLER Rotary Encoder (Single-turn) 19/22 4294967295
AD36-1219 / AD58-1222 HENGSTLER Rotary Encoder (Multi-turn) 31/34 1048576

Configuration requires that FB1.SELECT be manually set to 34, and that FB1.BISSBITS and FB1.ENCRES be set according to the values/equations in the table above.

Setting Up an Undocumented BiSS-C Encoder

  1. Configure the motor parameters properly. For linear encoders, make certain that the pole pitch is correct for the given motor.
  2. Refer to the encoder datasheet to determine the number of BiSS bits expected from the device. Use the terminal to set FB1.BISSBITS to this number.
  3. Under the "Settings->Feedback 1" tab, select "34 - BiSS Mode C Renishaw", then "Disable & Clear Faults". The encoder should now be returning data.
    1. If faults are being generated, first try Switching to "1 - None", the go back to "34 - BiSS Mode C Renishaw".
    2. If faults are still being generated, then the likely causes are:
      1. The FB1.BISSBITS value does not match the number of bits from the encoder. Recheck the datasheet & encoder
      2. There is a grounding issue and the communication lines are too noisy to return position data. Make sure the cable shield is correctly wired.
      3. The encoder may be using active high error bits instead of active low error bits. Verify this is not the case on the datasheet. For example, the LMA10 encoder series has active high error bits unless option 03 is used. As a result, non "option 03" LMA10 encoders will not work with the drive.
  4. Once the drive is communicating with the encoder and showing position feedback, the FB1.ENCRES (on some drives, FB1.ENCLINES) needs to be set.
    1. Use the table above to set FB1.ENCRES for known encoders.
    2. The general equation for linear encoders is: (pole pitch / encoder resolution) * 2^(32-BISSBITS). On 1.12.05.00 firmware, this will be (pole pitch / encoder resolution) * 2^(BISSBITS-32).
    3. Single-turn rotary encoders are always 2^32-1 = 4294967295.
    4. Multi-turn rotary encoders are always 2^(32 - (Number of Multi-turn bits)).
  5. If the encoder is still giving completely wrong position values, try working in reverse to determine the approximate value for ENCRES, then use that to verify your previous equation had the right input parameters. This is more useful when the encoder datasheet isn't entirely clear on what distance is measured by one LSB of the encoder.
    1. Set ENCRES to 65536 (2^16).
    2. Record the current position value in counts
    3. Move the encoder by one complete pole pitch or rotate the shaft one complete revolution
    4. Record the new position value in counts.
    5. Take the difference between the two, then divide by 65536. This is approximately what ENCRES should be.
    6. The encoder resolution is then approximately (pole pitch * 2^(48 - BISSBITS)) / (position 2 - position 1) for linear encoders.
  6. If, after trying all troubleshooting steps, the encoder is still returning incorrect values or does not work, please report the issue. Make sure to report which steps you were able to complete, what faults were generated, the exact model of the encoder, and a complete parameter dump from the drive.