Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Mon, 6 Feb 2006 17:33:48 +0100

On Sunday 05 February 2006 15:15, Tim Mooney wrote:
> John Dobbins wrote:
> >       aiRecord -> dfanoutRecord -> aoRecord
> >
> > I see this behavior when I make dfanoutRecord process:
> >
> > 1) aiRecord processes
> > 3) ao record processes writing the stale value, i.e. the value the
> > aiRecord had before it processed
>
> That's the way it's supposed to work.

I beg to differ. It may be well-documented (and historically 
understandable), but it still is an annoying and frustrating 
mis-feature, and definitely not how any sane person would expect it to 
work.

> it's a general
> feature of asynchronous processing.  A PP input link starts
> processing that will eventually return the new value, but just takes
> whatever value is there.  Otherwise it would hold up all the other
> records being processed by the same task.

Not if asynchonicity could be inherited via input or output links. Which 
would mean (1) every record support must support asynchronous 
processing and (2) we can pass a callback to dbPutLink resp. dbGetLink. 
That's it, mostly.

V4 was supposed to fix this limitation (and many others). Maybe this one 
would be a candidate for inclusion into some V3.16? I'll hapily 
volunteer to hack the IOC core to support this...

Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System