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Subject: Re: ai records: pool (SCAN) VS pull (FLNK) VS push (some examples)
From: Andrew Johnson <anj@aps.anl.gov>
To: Mark Rivers <rivers@cars.uchicago.edu>
Cc: EPICS mailing list <tech-talk@aps.anl.gov>
Date: Tue, 10 Dec 2013 14:35:14 -0600
Hi Mark,

On 12/10/2013 12:30 PM, Mark Rivers wrote:
> Also, if you are going to put a field in a FLNK it should not be the
> .VAL field, but rather the .PROC field, i.e.
> 
> field(FLNK,"$(user):AllInterlocksRdbk.PROC PP")

It is only necessary to name the .PROC field if the forward-link will be
connected over Channel Access, i.e. it points to a record in another IOC
or you have explicitly added a CA flag to it. Forward links which are
resolved as database links (the vast majority in most databases) will
ignore any field name you give. The CA flag is the only one that has any
effect on a forward link.

Benoit,

Your AllInterlocks record has SCAN set to "I/O Intr" so forward-linking
to it with a database link will not cause it to process. If you want it
to process on both I/O Interrupt and from the forward link, you will
have to make the forward-link a CA link, so Mark's suggestion above was
almost right.  Try this instead:

field(FLNK,"$(user):AllInterlocks.PROC CA")

If you want a deeper understanding of record links you might want to
take a look at my Database Principles lecture, which covers record links
from slide 22 on; the latest version is at
   http://www.aps.anl.gov/epics/docs/AES2011/07-Database.pdf

- Andrew
-- 
Advertising may be described as the science of arresting the human
intelligence long enough to get money from it. -- Stephen Leacock

Replies:
RE: ai records: pool (SCAN) VS pull (FLNK) VS push (some examples) Emmanuel Mayssat
References:
ai records: pool (SCAN) VS pull (FLNK) VS push (some examples) Benoit
RE: ai records: pool (SCAN) VS pull (FLNK) VS push (some examples) Mark Rivers

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