Familiar with FANUC servos? Reverse engineering serial encoder protocol.

**Yansii** · 05-03-2020, 08:08 AM

Hello,

I have a FANUC servo motor type "A06B-0117-B855#0049", that I would like to interface to some custom electronics. However, this is the newfangled stuff, with an encoder with a serial communication line. There are only six pins on the encoder available: A power supply 5V pair, backup battery supply pair and a communication pair of pins called "XPRQJ6 and PRQJ6". The motor came from I think the sixth axis from a Fanuc LR mate 200 iC robot.

I have stumbled upon this thread on CNCforum: https://www.cnczone.com/forums/fanuc...oder-info.html
That was the main inspiration to try reverse engineering it myself to repurpose the available parts.

However, my motor does not seem to fit the described protocol in the thread above.

There are several industry widely used serial encoder protocols, such es the Tamagawa T-format or Sanyo Denki / Nikon A-format. I have tried sending stuff at the encoder in these two formats, but failed, got no response. The internal encoder construction looks very familiar with the Tamagawa encoders from their catalogue. Please find below a photo of the encoder internals and the motor. Both of these protocols should default at 2.5Mbaud.

Does any of you have any info about what type of encoder it may be and what protocol it uses? Unfortunately I do not have any original servodrives available, so not able to sniff the original communication. Any info helps.

Thank you,
Yansi

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