I need to comunicate with two devices at the same time. The first is a PC with a Modbus Master running, obviously here the PLC act as a slave device (Modbus Slave), this communication works thru Port 0 with the Siemens Modbus Slave Library for S7-200. The second communication is thru Port 1 with an MM420 via USS protocol; the point is that the Simens USS Library for S7-200 works only with Port 0.

I downloaded Tip 28 (USS communication example) and I think I can modify it to work with Port 1.

I would like to know if this is posible? And if someone could give me some adviceses I’ll be thankful.