Experimental Physics and
Industrial Control System

Ben Franksen via Tech-talk <tech-talk at aps.anl.gov> · Tue, 16 Feb 2021 20:12:17 +0100

Am 16.02.21 um 17:53 schrieb Ben Franksen via Tech-talk:
> Am 16.02.21 um 17:10 schrieb Michael Davidsaver:
>> The use of "VAL" here confuses me, but I wonder "A&B&C&D=A|B|C|D"
>> should be "(A&B&C&D)=(A|B|C|D)"?
> 
> OMG, you are saying that this was a stupid operator precedence error? I
> will check that. (I had dismissed the idea that the CALC expression may
> be wrong since it works for weeks on end before failing.)

Embarrasing. That was the problem.

And the reason it did not lead to an error except if the timing is very
unusual is this: the input records are always processed in order, the
one connected to A first, then B, etc. If everything works correctly,
all inputs change to the same value in very rapid succession.
Incidentally, my broken CALC expression has the correct value after all
inputs change /in that order/. If the order gets messed up due to timing
glitches (these are CPP links), the result can be wrong though. In
particular, from A=B=C=D=VAL=1 one can set B=0,C=0,D=0,A=0 and all the
time VAL remains at 1.

Cheers & Thanks Michael!
Ben
-- 
I would rather have questions that cannot be answered, than answers that
cannot be questioned.  -- Richard Feynman

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System