Experimental Physics and
Industrial Control System

Andy Foster <[email protected]> · Wed, 25 Apr 2001 10:04:31 +0000

Hi Eric,

Yes, I noticed this too and have "spoken" (over E-mail) with 
Marty about it.

There are other records which exhibit the same feature, namely:
dfanout, stringout, steppermotor.

All have code similar to the longout with respect to the DOL
link. What I did was changed the longout and others to be like
this:

     if (!plongout->pact) {
             if( (plongout->dol.type != CONSTANT) && (plongout->omsl ==
CLOSED_LOOP)) {
                     status = dbGetLink(&(plongout->dol),DBR_LONG,
                             &value,0,0);
                     if (plongout->dol.type!=CONSTANT &&
RTN_SUCCESS(status))
                             plongout->udf=FALSE;
             }
             else {
                     value = plongout->val;
             }
             if (!status) convert(plongout,value);
      }

Then for a CONSTANT DOL type, the value gets initialized as it does
in an ao record.

Cheers,

Andy

Eric Bjorklund wrote:
> 
> I appear to have discovered a bug in longoutRecord.c under R3.13.4 which
> probably dates back to R3.13.3, when the drvh & drvl fields were added.
> 
> The manifestation is that a longout record with OMSL in closed_loop and
> a constant value in the DOL link, will end up with an arbitrary value
> in VAL when the record is processed.
> 
> The culpret is in the following code from the "process" routine:
> 
>     if (!plongout->pact) {
>             if (plongout->omsl == CLOSED_LOOP) {
>                     status = dbGetLink(&(plongout->dol),DBR_LONG,
>                             &value,0,0);
>                     if (plongout->dol.type!=CONSTANT && RTN_SUCCESS(status))
>                             plongout->udf=FALSE;
>             }
>             else {
>                     value = plongout->val;
>             }
>             if (!status) convert(plongout,value);
>      }
> 
> If dol.type is CONSTANT, dbGetLink does not fetch the link value, and so
> the variable "value" is never initialized.
> 
> The fix, I've implemented for now is to initialize "value" in its declaration
> at the begining of the process routine, i.e:
> 
>         long             value=plongout->val;
> 
> This restores the longout record to its previous behavior -- which is not
> the same as, for example, an ao record with the similar setup since it
> allows you to change the value by writing to the VAL field.  For that, however,
> we'd probably have to add another field to longout (such as the ao's PVAL
> field).
> 
> Eric Bjorklund
> LANSCE-6 Controls
> Los Alamos Neutron Scattering Center.
> [email protected]

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System