Experimental Physics and
Industrial Control System

Stephanie Allison (415)926-4534 <[email protected]> · Wed, 9 Oct 1996 9:23:30 -0700

>Last week during a visit at DESY, Gabor Csuka
>suggested that the ai and ao records should have two additional
>fields RAWH and RAWL. The reason is that often it is possible
>to create common device support for a set of modules that differ
>only in the number of bits and/or polarity.

This sure would simplify ai device support for the Allen-Bradley
Direct Communication Module (1771-DCM) where the people writing
into the DCM promise they will always write unsigned 12 bit values,
except when they don't (oh yea, that's a 16 bit signed value...).

Instead of RAWH and RAWL, I'd prefer a MASK and SIGN field used by 
device support in updating RVAL.  In my case, MASK would be the
bits used (0x0FFF for a 12 bit value) and SIGN would be either 
0/1 for unsigned/signed or a mask of the sign bit in RVAL.  But this 
probably goes too far toward the "unlimited set of configuration 
fields" problem.  No need to comment on this.

I assume that if RAWH and RAWL values change, a special SPC_LINCONV
will be done to get an updated ESLO (like is done when EGUF and EGUL
is changed).

Stephanie

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System