I assume you are using our Super PLC - Nano10, FMD, F-series or T100MD+.
Then you just need to run the following statement once during startup:
SETBAUD 1,3
this will set the PLC's RS232 port to 9600 bps, 8 data bit, 1 stop bit, no parity. Hardware handshake is not used by any of our PLCs.