Fanuc encoders

I have the incremental encoders in my lathe, they are the beta versions
however. On these encoders the 10-bit absolute position is there and
accurate enough to use for commutation right from the start. There is
a step in this data however once the encoder passes the index.

The control computer had a backup battery, the battery connection of
the encoders was not used. So I assume the computer was responsible
for remembering the position. There are no homing sensors on the lathe,
so I guess they ran the lathe to its endstops when the battery failed.

For me the hard part was to get the encoder to respond. It wants a
positive pulse on the REQ line, and initially I was trying a negative
pulse. After that, verifying the encoder position was simple enough with
a scope indeed.

The nice part about the CRC is that there are only 32 possible
polynomials, so bruteforcing works like a charm

I hope my information helps someone, but if not... nothing is lost.
I doubt reading the VHDL and C code of hostmot2 would have been faster
than what I did, but I certainly would have tried it, if had known about
it. On the other hand, the microcontroller I use can only capture frames
up to 64 bits, so knowing the padding are actually start and stop bits
was crucial.

On all the encoders, after power-on, there is a step in the high-res data when the encoder passes the index position. But, there is NO step in the low-res absolute data. My converter board FPGA makes the high-res step disappear as it converts to quadrature. I know WHY Fanuc went with the serial scheme, the quadrature count rates become insane when you start thinking about 1 million counts/rev, and so converting those to quadrature is not practical at full resolution.
Jon

for Fanuc Encoders you can check here panasonicservomotor.com/fanuc-encoder . include code Fanuc code list

That is just a list of error codes produced by the Fanuc control. I have a working converter for the 4-wire, low speed (1.024 mbit/second) encoders. I am now trying to decipher the 2-wire, 2.73 mbit/sec encoders. I have been able to trick an encoder to start responding by flipping switches on a pulse generator. But, I tried to set up an FPGA to get the encoder to respond, and I get NOTHING!
So, these encoders apparently need a different command to select the mode before it will respond.
Jon