Alan,
Thanks a lot, I do need more info.
First, we have about 77 SDI (serial DI), 3 SDO, 23 SAI and 5 SAO per each slave PLC connected to the Master (ControlLogix) and you can see total serial IO numbers (77+3+23+5)x3=324 is more than hardwired IO (121DI+31DO+37AI+10AO or 199), so the serial communication is very important in our case.
Second, I didn't find DF-1 port in Kingfisher catalogues, which processor did you use before?
and finally, can you send me a link/document to getting more familiar with serial I/O communication and its requirements (networking, hardware/software)?
Thanks,
Soren