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Good day,

 Can't get to work my application.. I have a V350 PLC connected through GPRS modem as  TCP/serial converter and InTouch scada on the other side. Tried DASMBTCP v1.0 and v3.0 and can't get any value from PLC. Modbus Poll (software) and other modbus TCP testers work well. Doing DAServer and Access name configuration according manual, but no success. What could be wrong?

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  • 2 weeks later...
  • MVP 2023

We've run into this problem communicating over modems.  Your packet timeout is too short on the PLC side.

Little known SI parameter - SI 101 TCP/IP retries base timeout.

Factory defaults to 2 (200 ms).  If you're on a local network this is plenty of time.  Our testing with two GPRS modems and Wireshark showed a typical initial packet transition time of 500 ms through the cellular system.  Your PLC is hanging up on the SCADA system.

Set SI 101 to 10 and see what happens.

Joe T.

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