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<== Date ==> <== Thread ==>
Subject: Re: Problem with a calc record
From: Ralph Lange via Tech-talk <[email protected]>
To: EPICS Tech Talk <[email protected]>
Date: Tue, 28 May 2019 13:40:28 +0200
The behavior depends on what the s7nodave driver does.

The caveat is:
Input links that PP point to input records with asynchronous device support will always read the current value and trigger the record to process, so the record reading the link will see the "old" value, and the new value (that was acquired as a result of the asynchronous processing) is not seen.

In such situations, FLNK is your best friend, because in records with asynchronous behavior, FLNKs are triggered during the second phase processing (i.e. after the new value was read).

Still, for an alive counter, I would expect the input record to be "I/O Intr" scanned, so that every step of the counter is seen. Then the watchdog calc record can do whatever it prefers to see if things are still moving, e.g. scan periodically and use an NPP input to check the alive counter differs from the last time, before saving the current alive counter value in another field.

Cheers,
~Ralph

References:
Problem with a calc record CAPOBIANCO Roberto via Tech-talk
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