Experimental Physics and
Industrial Control System

Luedeke Andreas <[email protected]> · Wed, 20 Oct 2010 11:08:50 +0200

 Di Maio Franck wrote on 18/10/10 14:56:
> A typical ITER use case:
>
> "Do A at time T", 
> - T: a setting controllable by PV(s),
> - A: an action implemented by a record triggered by an event occurring at time T
I'm not sure I fully understood the question, but here are my thoughts on it
anyway :-)

In a distributed control system you'll need to synchronize your actions over
many different IOCs.
To do that, the IOC time is not a particular good choice,
since the time in nanosecond will may not be the same on all IOCs.
Unless you use a specialized timing system.
And if you use a timing system anyway, you would rather create events to cause
actions.

If you distribute events over your timing system to cause synchronized actions,
you may want
to create those events based on absolute timestamps on the event generator IOC.
Is that what you intend to do?
Most accelerators don't need that, you rather create the events in fixed
frequencies and
enable or disable the whole sequence of events on demand.
Is anyone out there creating events based on absolute timers like
"push event T on the 20th of October 2010 at 20:10:20.102010"?

To implement this, the controllable "A" would just listen to a timing event to
be received by the Event-receiver.
The time "T" to create the event would be defined by the Event-generator, either
in soft or hardware.
If you are talking about events over a very long time range with high absolute
time precision,
you would probably rather look for specialized timing hardware.
If you are talking about relative timing within some seconds to some master
event with nanosecond precision,
most sequences can likely be created by software on the event generator.

I hope some of the ideas were not completely off topic.

Regards
Andreas

-- 
For every complex problem, there is a solution that is simple, neat, and wrong.
                -- H. L. Mencken

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System