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<== Date ==> <== Thread ==>

Subject: RE: autosave - different PV to read and write
From: Mark Rivers via Tech-talk <tech-talk@aps.anl.gov>
To: 'Ryan Pierce' <rdpierce@pobox.com>
Cc: "'tech-talk@aps.anl.gov'" <tech-talk@aps.anl.gov>
Date: Tue, 20 Aug 2019 15:16:39 +0000
Hi Ryan,

> I'm wondering if it is possible to configure autosave to read one PV and record its value in a save file, but on recovery, to write that value to a different PV

I don't think you can do that with autosave.

If the driver was written with asynPortDriver then you could simply remove the PZ from autosave.  The driver would read the PZRBV into the same parameter during initialization.  The PZ output record would do an initial read of the parameter value, and set PZ to that.  This is part of the "bumpless reboot" feature of asyn device support, meaning output records can get their values from the hardware when the IOC starts up.  If there are autosave values then they will then override that initial value.

However, the Canberra ICB support predates asynPortDriver and does not work this way, PZ and PZRBV are not linked as they should be.

However, you can still easily achieve what you want.  You just add another record to your database.

record(ao, "$(P)$(AMP)SyncPZ") {
    field(DOL, "$(P)$(AMP)PZRBV")
    field(OMSL, "closed_loop")
    field(OUT, ""$(P)$(AMP)PZRBV PP")
    field(PINI, "YES")
}

This record will process once at iocInit.  It will read the value from PZRBV and write it to PZ.

Mark

-----Original Message-----
From: tech-talk-bounces@aps.anl.gov <tech-talk-bounces@aps.anl.gov> On Behalf Of Ryan Pierce via Tech-talk
Sent: Tuesday, August 20, 2019 8:31 AM
To: tech-talk@aps.anl.gov
Subject: autosave - different PV to read and write

I'm wondering if it is possible to configure autosave to read one PV and record its value in a save file, but on recovery, to write that value to a different PV. I am thinking along the lines of the .req file containing both the PV to read and the PV to write in the case where it would be different.

Example: The Canberra ISC amplifier can be placed into a mode where it automatically determines the Pole Zero value based on the input signal. 
This can be done once, and the measured value can continue to be used (assuming the detector or shaping time aren't changed.) If the IOC restarts, it would be helpful to restore this along with all the other settings. This can be read from $(P)$(AMP)PZRBV but it must be set in $(P)$(AMP)PZ

I'm guessing the concept of one PV to write with a separate readback PV is common. Has this been addressed, or is there a need for this?

Regards,

Ryan



References:
autosave - different PV to read and write Ryan Pierce via Tech-talk

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