Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Wed, 22 Apr 2009 23:35:59 +0200

On Mittwoch, 22. April 2009, Leicester, PJ (Pete) wrote:
> What I need to do is propagate this error state back to the 
> mbbo records so that it is visible on the edm screen.

It is funny that you ask this because just today I had the "inverse" 
problem: I had a record that for no obvious (to me!) reason went into 
LINK/INVALID state. I checked and re-checked again all the input links and 
all links pointing to my record and found nothing INVALID and no broken 
links.

I found the solution to this riddle when I noticed that the record has an 
output link with PP option and that my first record does /not/ become 
LINK/INVALID if the second one (an ao record) gets disabled. Now the second 
record's OUT link is indeed broken and this seems to result in its 
processing returning an error so that dbPutLink (from the first record) 
thinks that it has failed when in fact the value gets transported just 
fine, only the processing of the target record fails. Whereas if the second 
record is disabled, processing is successfully "not done" so the dbPutLink 
in the first record succeeds ;-)

This is probably well known, maybe even documented, and (arguably) correct 
behaviour. Yet it's a pitfall that took me some time to figure out.

Cheers
Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System