Re: EPICS periodic scan and sysClkRateSet()

[David Maden <David.Maden@psi.ch>]

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

                               David.Maden@psi.ch
     _/_/_/   _/   _/_/_/     Beamline Control Group, SLS Project
    _/       _/   _/         Paul Scherrer Institute
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