Well, I have the first cut at the Fanuc absolute encoder test unit working. I pretty much verified what I got off the oscilloscope, but in better detail. I am guessing there may be other commands that can be sent to the encoder to get other data and functions. But, anyway, what this particular unit provides is : A 15-bit angular position count and a 14-bit revolution count that are reset the first time the index position is passed. This can be read as a contiguous 29-bit signed binary number. A 15-bit unsigned angular position that is relative to where the encoder was when power was turned on. This does not reset when it passes index. These counts both have a bunch of LSB zeros to accommodate encoders with higher resolution. There seems to be an encoder model ID at the beginning and a 4-bit checksum at the end. I didn't find any sign of commutation info in the data stream I am getting now, so it would be hard to make a servo drive move the motor to the index position during the homing operation. But, I have seen the traditional Fanuc C1-C2-C4-C8 commutation signals on the encoder's PCB test points, so there probably is a different command that will make it send this info.
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