Slave not responding

[ruciuPL]

I am using NModbus to connect PC (master) to a PLC (slave).
Everything runs perfect until PLC goes to STOP or ERROR - the connection remains, however the Modbus Slave is not responding.
I am using ReadMultipleRegisters function. The telegram is sent to PLC but there is no response and program is waiting for response. Is there a response timeout method to use? Should I do it any other way?

[MichaDit]

Yes, you have to set the timeouts for e.g. tcpclient - this is out of scope of NModbus lib.

[ruciuPL]

I am thinking about using a timer to check if "response" is != NULL. Should it work? How should I perform a "break" (or similar) istruction for a higher-level function (I am out of date in c#)

[MichaDit]

There are built-in functions for that.
For TcpClient set ReceiveTimeout and SendTimeout.
For SerialPort set ReceiveTimeout.

[ruciuPL]

Thanks, I will try it ASAP

[ruciuPL]

Another issue... If a PLC goes to STOP and return to RUN when I send data to it the "slace busy" exception occurs and blocks the whole program (in this case only Modbus in PLC is stopped, the TCP/IP layer is running). I have no idea how to manage this.