Emerson Exchange 365

M Series Serial Card - Series 2 | Bad status | Reads work and writes don't?

Stumped on this one.

On one of our serial cards, we have Port 2 running as a Modbus RTU slave, RS232, 9600 8N1

This is connected to a Lantronix device that functions as a Modbus Serial to TCP gateway.  The Modbus TCP master\client sits on the other side performing read and write functions to the DeltaV array of holding registers.

We have partial functionality and that is where I am confused.
The master can read the holding registers and I can see other data being written back when viewing the input dataset registers in diagnostics.
However, the Status of the port is "Termination Lost" and my input parameters in DeltaV are also 'Bad"  (values mapped to the registers that are being written to by the modbus client)

So DeltaV data is being delivered to the holding registers supplied by the serial card and the master can read these values.
Writes from the master back to the slave show up in diagnostics but not in DeltaV.

Invalid String

• 19 Aug 2023 8:14 PM
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2 Replies

• Matt Forbis

  

  • 21 Aug 2023 1:29 PM

  There is a fairly old KBA NA-0800-0066 that addresses Termination Lost when not using hardware handshaking. This says put a jumper between DTR and DSR on the DeltaV serial card (For port 1, terminals 7 and 8, for port 2, terminals 15 and 16). Hope this helps clear up the error first (and maybe the other issues as well.)

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• Invalid String

  

  • 26 Aug 2023 8:21 PM

  In reply to Matt Forbis:

  Thanks Matt!
  I installed the jumper and serial comms are looking great now

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