Experimental Physics and
Industrial Control System

I’m not convinced that any changes are really needed. I don’t want us to add another menu field for this, and I see Heinz’s somewhat unusual problem as a corner case that we have other ways to solve without changing the code.

Heinz, can you tell us whether my solution using IVOV or Ralph’s meets your needs please? I think we need to hear from you to stop alternative ideas from proliferating.

Thanks,

- Andrew

On Jan 29, 2021, at 10:19 AM, Ralph Lange via Core-talk <core-talk at aps.anl.gov> wrote:

On Fri, 29 Jan 2021 at 15:57, Ben Franksen via Core-talk <core-talk at aps.anl.gov> wrote:

Am 28.01.21 um 14:20 schrieb Zimoch Dirk (PSI) via Core-talk:
> One could of course change the check to if ((prec->drvl !=0 || 
> prec->drvh !=0) && prec->drvh > prec->drvl) But then in ao as well.
> 
> It would change traditional behavior (which used to be documented 
> wrongly in earlier EPICS releases) and potentially break existing 
> IOCs where people use DLRH = DRVL != 0 and expect the limits to be 
> ignored. It would also introduce a new "special case" because the 
> record can then be fixed to any value except 0. Another option is to 
> change the defaults from 0,0 to -verybig,+verybig.
> 
> I think a poll would be needed.

-1

This makes a bad situation worse by complicating the rules. The problem
is the use of in-band exceptional values which is bad design and will
invariably hit you back sooner or later. Better fix: add a new field to
select whether to use or ignore DRVH/L.

To keep compatibility, that would have to be a menu AUTO/NO/YES with a default of AUTO.