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<== Date ==> <== Thread ==>
Subject: Re: EPICS periodic scan and sysClkRateSet()
From: David Maden <[email protected]>
To: EPICS tech-talk <[email protected]>
Date: Mon, 17 Nov 2003 09:57:18 +0100
Steven Hartman wrote: 
I have a few questions concerning the periodic scan rate in EPICS and the
VxWorks system clock rate. I am currently working with EPICS 3.13 on
VxWorks 5.4, but would be interested if there are significant differences
in 3.14.

 - Is there anything in base which may break or otherwise behave
differently if the VxWorks system clock is increased to be faster than 60
Hz? ...

Another small addition to the other responses ...

If you change the clock rate, be careful with the "delay" function of the sequencer, at least with version 1.9.2.Beta12. The argument is no longer seconds if the tick rate is not 60 Hz. It is necessary to use code of the form:

%% #include <sysLib.h>

float tickFactor;

       ss snlProgram {
         state pre_init {
           when () {
             tickFactor = sysClkRateGet ()/60.0;
           } state init
         }
         state init
           ...
           when (delay (<secs> * tickFactor) {
             ...

We use a clock rate of 250 Hz on our diffractometer stations at the material science beamline and have noticed no performance problems.

Regards,

David Maden

                               [email protected]
     _/_/_/   _/   _/_/_/     Beamline Control Group, SLS Project
    _/       _/   _/         Paul Scherrer Institute
     _/_/   _/     _/_/     CH-5232 Villigen-PSI
        _/ _/         _/   Tel: +41 56 310 3616
   _/_/_/ _/_/_/ _/_/_/   Fax: +41 56 310 3294

Replies:
Re: EPICS periodic scan and sysClkRateSet() Steven Hartman
References:
EPICS periodic scan and sysClkRateSet() Steven Hartman
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