Experimental Physics and
Industrial Control System

Ben Franksen <[email protected]> · Tue, 30 Sep 2008 21:33:55 +0200

On Dienstag, 30. September 2008, haquin wrote:
> 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 have no good answer for your question about diagnosing PACT state, but 
there is one thing you could do that might help solve your lost-writes 
problem: You can use "Async Soft Channel" support for the record that 
writes through the link. This will make the writing record asynchronous if 
the target record is, i.e. it will remain active (PACT=1) as long as the 
target record is active. OTOH, depending on your application this might 
merely push the problem upwards...

Cheers
Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System