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<== Date ==> <== Thread ==>

Subject: Re: Variable scan rate
From: Emmanuel Mayssat <emmanuel_mayssat@lynceantech.com>
To: Steven Hartman <hartman@fel.duke.edu>
Cc: EPICS tech-talk <tech-talk@aps.anl.gov>
Date: Thu, 05 Jan 2006 10:53:20 -0800
There are several cases in which I may want to slow down ( and even
stop ) scan rates.
1/ debugging purpose
	Debugging messages are displayed each time the record 
	is processed. When my Ioc crashes I do not want to be flooded
	with debugging information. Ultimately I want to see only the
	debug info of the record that crashed the ioc.
2/ overload of an ioc
	I want to put as many devices on an ioc as possible
	so I need to minimize record processing.
	That is one way to improve uptime and lower cost 
	of control system 
3/ Bus conflict
	There are also bus conflict I want to minimize 
	(several devices on same gpib bus, etc. )
4/ temperature can be read by another more accurate device
5/ temperature cannot change due to external factors. Granted that
regulation may fail due to a failure of the regulating device itself, in
that case we have a device alarm that trip.

The thermo regulator device I was referring to complies with all of the
above.  

Anyway what is interesting to me at this point is to change scan rate
from high to low. I want to see the readback transition at high
resolution and slow the scan rate once everything stabilize.

I like the NPP & PP trick in the calcout.
The sequencer is also a great solution.
Now I can pick between a value based versus a time based solution. 

Many thanks for your input,

--
Emmanuel Mayssat


On Thu, 2006-01-05 at 12:37 -0500, Steven Hartman wrote:

> be set by the operator using an MEDM "menu" button. But for something like
> the temperature readback, I would just leave it at the fast rate all of
> the time.



Replies:
Re: Variable scan rate Steven Hartman
References:
Building JCA1 John Faucett
Variable scan rate Emmanuel Mayssat
Re: Variable scan rate Steven Hartman

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