Yes, you can select the MODBUS RTU protocol in the Maple System for use with the TRi's M-series PLCs. If your Maple OIT is equipped with 2 wire RS485 you can connect it directly to the PLC's COMM3 port and use the MODBUS RTC (485 2W). I am not certain about the 1st protocol you mentioned, but I suspect it should work over a RS232 connection too. Just make sure that the serial settings of two sides match each others. The default is 38400, 8 data bit, 1 stop bit and no parity. The default PLC's ID is = 00.