RE: DB Question

[<nick.rees@diamond.ac.uk>]

IIRC (I don't have the code in front of me at the moment) the way to override this asyn behavior is to set OMSL to Closed Loop and DOL to a constant value.

Cheers,

Nick Rees
Principal Software Engineer           Phone: +44 (0)1235-778430
Diamond Light Source                  Fax:   +44 (0)1235-446713

Mark Rivers <rivers@cars.uchicago.edu> wrote:
Hi Zen,

Remember that standard asyn device support for output records does the following at iocInit:


1)      Attempts to read the current value from the asyn port driver

2)      If that read returns asynSuccess then the VAL field in the record is replaced by the one read from the driver

3)      If that return does not return asynSuccess then the VAL field is not modified

This behavior is designed to support “bumpless reboots”.

I suspect your driver is returning asynSuccess on a call to asynInt32->read() at iocInit.  If you want to preserve the value of the VAL field from the database file then your driver must not return asynSuccess.

Mark


From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Szalata, Zenon M.
Sent: Friday, November 16, 2012 10:32 AM
To: tech-talk@aps.anl.gov
Subject: DB Question

Hi,
I am a bit confused by the following behavior.
I am using EPICS R3.14.12.2 and asyn R4.20.
I have a simple longout record:

record( longout, "$(P):$(N):LO:BTOI:NCOEF"){
  field( DESC, "N Coefs:")
  field( DTYP, "asynInt32")
  field( OUT,  "@asyn($(PORT),$(N),1)LO_NCOEF")
 field( VAL,  "2")
  field( PINI, "1")
}

After this record is done initializing, caget on it gives me 0.

I have introduced another record as follows:

record( longout, "$(P):$(N):LO:NCOEF"){
  field( DESC, "N Coefs:")
  field( VAL,  "2")
  field( OUT,  "$(P):$(N):LO:BTOI:NCOEF PP")
  field( PINI, "1")
}
record( longout, "$(P):$(N):LO:BTOI:NCOEF"){
  field( DESC, "N Coefs:")
  field( DTYP, "asynInt32")
  field( OUT,  "@asyn($(PORT),$(N),1)LO_NCOEF")
# field( VAL,  "2")
#  field( PINI, "1")
}

With these two records the second one now has the correct value.
Why does the single record solution lose its VAL value?

Thanks in advance,
Zen

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