Experimental Physics and
Industrial Control System

Ken Evans <[email protected]> · Wed, 23 Sep 1998 11:58:09 -0500 (CDT)

     I wasn't exactly right when I said MEDM only looks for HOPR and
LOPR.  More accurately, it calls ca_array_get_callback() for the
process variable in question and specifies a callback to run when the
graphical information is sent.  The information returned to the
callback is obtained (by Channel Access) by calling the
get_graphic_double() routine in the record's record support.  What is
returned is whatever the record support decides to return.  In most
cases this is HOPR, LOPR, and PREC.

     In the case of the Histogram it should probably be ULIM, LLIM,
and I'm not sure what for PREC.  The real problem is that Ned Arnold
has checked, and the Histogram, apart from using unusual names for
what should probably be HOPR and LOPR, doesn't have a
get_graphic_double() routine in the record support.  Consequently what
is returned to MEDM is undefined (read garbage).  This does tend to
foul up MEDM.

     It is my understanding, mostly from Marty Kraimer, that the
Histogram record was developed here but never really finished because
some of the people involved left.  It is not used here as far as I
know, and I am not very familiar with it.  I just created one, but I
don't understand it completely.  It doesn't seem to work exactly as
the Record Support Manual says.  Janet Anderson, who would know more
about it, is not here today.

	-Ken

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System