5i25 + 7i74 -> 4 Smart Serial + 4 SSI Encoders

You might be able to work out the framing from the STMBL driver:

github.com/rene-dev/stmbl/blob/master/src/comps/yaskawa.c

It does appear that there is a crc to worry about.

I already explained this on emc-users: sourceforge.net/p/emc/mailman/message/36930203/

It doesn’t work because it’s not ssi.
Its hdlc over Manchester over rs485.
I fully reverse engendered the protocol(including crc).
Stmbl has support for yaskawa encoders, there is some documentation in the code.

github.com/rene-dev/stmbl/blob/master/src/comps/yaskawa.c

Line 89 is the request. You can use only the f4 part of the stmbl, and convert the signal to sserial.
Or just use a stmbl.