Experimental Physics and
Industrial Control System

Haquin,  You can read the PACT field immediately before processing
the calc record, and have the waveform record forward link to a
record that clears the value you just read.  This may produce
some short-lived false positives, because it's possible for the
waveform record to complete between the read of its PACT field and
the processing of the calc record.

Hi all,

Here is what I do:
a Calcout record output its value into the VAL field of a Waveform record (using a Process Passive link triggering the processing of the Waveform).
Then the Waveform record performs a Modbus/TCP write access with Asyn/Modbus device support.

My problem is the following:
Sometime though the last value is in the VAL field of the Waveform record it is not written via Modbus.
I have already investigated on the Asyn/Modbus side, but it turns out that when the problem occurs Asyn/Modbus is not even called.

It seems that the problem occurs when the Calcout record requests the Waveform record for a new Modbus write access but the Waveform record is still busy with the previous one...
Can someone explain me how to be warned or informed when the processing request of a record is ignored because it is still busy (PACT=1).

I tried setting field TPROC=1 to check if the Waveform trace is missing when the problem occur,
but this is intrusive and the problem is then not reproducible...

thanks.

--
Tim Mooney ([email protected]) (630)252-5417
Beamline Controls & Data Acquisition Group
Advanced Photon Source, Argonne National Lab.

References:

How to be warned when a record processing is ignored because already busy (PACT=1) haquin

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