Unfortunately, both the original poster or myself know anything about the Keyance unit. At a guess as it has 3 bar code readers it may need to be polled if so then obviously there is some work to do in creating the send requests from the FX, however, it could send all 3 i.e. as an address followed by data from bar code 1 then an address bar code 2 etc. in this case it could be one long string. In this situation if it is not required to send a request the FX 232 card will just accept all communications packets without requests. I have used both situations one was a scale that continually sent a string representing the weight, all I had to do was wait until the chars rxd register had a value > 0 (or Wait until > x chars as this was a fixed string length) then read the receive buffer to extract the weight value. The other was a bit more challenging it wrote values to a stepper drive and received controller data, however this wasn't a big deal, it did require a fair bit of code for the polling etc. but was small compared to the rest of the PLC program.
