Experimental Physics and
Industrial Control System

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Randall Cayford via Tech-talk <tech-talk at aps.anl.gov>
Date: Friday, January 14, 2022 at 3:18 PM
To: Gofron, Kazimierz via Tech-talk <tech-talk at aps.anl.gov>
Subject: FLNK doesn't process

I have a periodic scanned PV which I occasionally set.  However, when I set it, I can’t read the updated value until the periodic scan happens.  I would like the PV value to update as soon as it’s set.  I thought that was what was supposed to happen with FLNK but it doesn’t seem to.

My db has:
record (ai, "$(P):current1")
{
    field (DTYP, "stream")
    field (INP, "@thorlab.proto getcurrentch(1) $(BUS)")
    field (SCAN, "10 second") 
}

record (ao, "$(P):setcurrent1")
{
    field (DTYP, "stream")
    field (OUT, "@thorlab.proto setcurrentch(1) $(BUS)")
    field (FLNK, "$(P):current1.PROC")
    field (SCAN, "Passive")
}

"caput setcurrent1 10" works but it takes whatever is left of the 10 second scan period before current1 changes.
“caput current1.PROC 1” immediately updates the value in current1.

I tried     field (FLNK, "$(P):current1”) but that doesn’t process either.

What’s the trick for getting a periodic scan PV to process within a forward link?  Or is there some other way I’m supposed to do this?

Thanks.

Randall
LBNL