The DE-9 version was before my time (in development terms) I think it used RS485 and a Z8530 but the 4Mbps speed feels a bit quick for those technologies. I ca

The DE-9 version was before my time (in development terms) I think it used RS485 and a Z8530 but the 4Mbps speed feels a bit quick for those technologies. I can still remember the prefix 00802C which we used for Ethernet addresses and at one point I ended up decoding Ethernet packets from an oscilloscope to make sure we were getting the CRC calculation correct. There are a few ways to compute a CRC and some books incorrectly say that starting the shift register with all ones is the same as inverting the first 32 bits into the register, I suspect this is because the error detection effect is the same. Somewhere I probably have a card or two and I might have the schematics lurking around but they'll be in the basement somewhere.