Experimental Physics and
Industrial Control System

Gerrit Kühn via Tech-talk <tech-talk at aps.anl.gov> · Wed, 6 Dec 2023 07:46:59 +0100

Am Wed, 6 Dec 2023 03:46:58 +0000
schrieb "Johnson, Andrew N." <anj at anl.gov>:

Hello Andrew,

Thank you very much for this in-depth explanation. 

> The record's SCAN field is set to "I/O Intr", and in that case the
> dbProcess() call on line 1273 will not be made because the PP attribute
> on the VAL field only makes the record process when it has SCAN=Passive.

This (the *only* part) indeed was what I was not sure about from reading
the documentation. Thanks for the clarification.

> You already found the workaround for that in your next email,

Is this the solution one should go for in that case?

> and this is
> the answer to your later question about the documentation, when it talks
> about Passive records it does mean that the processing only happens when
> SCAN=Passive. It doesn't mention other SCAN types and they don't get
> processed by the PP mechanisms.

Maybe adding the word "only" there would make this clearer.

> Rolf Keitel's description thus applies to your later ai records, but not
> to the I/O Intr record itself. I believe there are only two ways that an
> I/O Intr record can get processed; by an interrupt from device support,
> or when something puts a value to its PROC field. The latter can happen
> by many mechanisms though, e.g. DB link, CA link, CA client, PVA client,
> dbpf etc.

This is another potential solution (I didn't try yet): My second update
path for the I/O Intr record (apart from receiving real new data from
device support) is coming in over a dfanout record (that also writes to
the other passive records). There are free output links, so it should be
possible to use one of them to write to the .PROC field (while using a
different one to update the .VAL field)?

cu
  Gerrit

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System