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

Subject: Re: mbboDirect record and SHFT field
From: Ralph Lange <[email protected]>
To: EPICS Tech Talk <[email protected]>
Date: Fri, 15 Sep 2017 11:31:11 +0200
FWIW,

The Base commit logs show a commit labelled
SHFT was made a prompt field and also modifiable. The VAL field of mbboDirectRecord is now modifiable.
done by Marty Kraimer on September 29, 1998, which was released in 3.13.1.1 and 3.14.0.
The change is mentioned in the release notes of R 3.13.1

So, yes: the docs seem to have been out of sync for a little while.

Cheers,
~Ralph


On Wed, Sep 13, 2017 at 11:22 PM, Rod Nussbaumer <[email protected]> wrote:
We're looking at device support written by a vendor, and there is a database template that includes in a mbboDirect record with the .SHFT field given a value in the EPICS runtime db. Since our database configuration tool, tdct, doesn't provide for creating a DB with the SHFT field set for that particular record type, I started looking...

In the record reference manual for 3-14 record reference manual, it says "the SHFT value is set by device support and is not configurable by the user". The information in the accompanying table supports this, indicating in the 'DCT' field of the table 'NO' for the SHFT field of the record type.

In the R3.14.12.3 dbd file for the mbboDirect, there exists the entry "promptgroup(GUI_MBB)", suggesting that a database configuration tool should be allowed to set the SHFT field. When the database is loaded on an IOC, and the SHFT field has been initialized at dbLoadRecords time, the field behaves as one might expect for that circumstance.

Is that the intended behavior, and the docs are out of sync, or the other way around?

If the SHFT field should really only be set by device support, is there a strong convention for that? The method I recall is to infer from a bitmask supplied in the .OUT field, by counting the number of clear least significant bits. Are there other conventions or preferences?

Rod Nussbaumer
Group Leader, Controls
TRIUMF
Vancouver, Canada


References:
mbboDirect record and SHFT field Rod Nussbaumer

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