Experimental Physics and
Industrial Control System

[email protected] · Tue, 9 Apr 2002 10:55:26 -0500 (CDT)

re...,

> Some users here at LANL had a suggestion that's actually useful.
>...
> The problem is about entering "wrong" values from a GUI,
> that is values outside of [DRVL, DRVH].
> Per default, the AO record would "clamp" the value, e.g.
> Value > DRVH    ==>   value = DRVH.
> 
> This can lead to jumps. Example: [DRVL,DRVH]=[0...10], current value 0.5.
> User wants to make it 0.6 but accidentally enters 60
> ==> You jump to 10. That's a big jump from 0.5!
> Just staying at 0.5 and allowing the user to try again
> might be better.
>...
> Solution: New AO field DRLM - "Drive Limit Mode"
> Possible Values:
> 
> a) "Clamp" (default)
> As before, any value outside of DRVL ... DRVH
> is clamped/changed to DRVL or DRVH.
> 
> b) "Reject"
> Any value outside of DRVL ... DRVH
> is rejected. The record returns to the
> previous value (still available in the OVAL field).

That would be nice.  I'd even argue that "reject" should become the
default.  It would be confusing, though, if you wrote "10.0" to a
record whose DRVH appeared (PREC=1) to be "10.0" but actually was
"9.996".  A user would want some indication of why the value was being
ignored, or they'd just reboot the crate and claim EPICS had "crashed".

Tim Mooney ([email protected]) (630)252-5417
Beamline Controls & Data Acquisition Group
Advanced Photon Source, Argonne National Lab.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System