hi, i am using omron cpm1a plc in a project in which i have to communicate it to thinget op 20 which follows 232 protocol the problem is, the communication port in omron cpm1a has 20 pin d type connector i just want to know the tx rx nd gnd pin in that port so that i can make a null modem cable to communicate it with op i have searched a lot the only thing i found was c1f01 adapter which gives out through a lot easier db9 port in that case also what is the purpose of that adapter if it is simple 232 communication