Experimental Physics and
Industrial Control System

Steven Hartman <[email protected]> · Fri, 14 Nov 2003 12:37:03 -0500 (EST)

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? Looking at dbScan.c, it looks like the periodic scan rate will do the
right thing (so long as sysClkRateSet() is called before initPeriodic(),
so before iocInit()). drvTS.c also looks OK. Anything else in base that
may be a problem? (I will of course check device code, sub records, etc
which are used in the app which are not in base.)

 - Does anyone have any experience on a reasonable limit to the fastest
periodic scan rate which is practical? I will likely be using a 450 MHz
MVME-5100 PPC. The answer to this question will be processor and
application specific, and would require some trial and error, but it would
be useful to have a rough estimate based on other's experiences.

 - Does anyone have experience on a maximum reasonable VxWorks clock rate
with an EPICS application? Same caveats as above, but a rough guideline
would be useful.

I don't yet have the ppc boards for testing (just mv167's), so this info
will be useful for planning purposes.

Thank you,
-- 
Steve Hartman
[email protected] | 919-660-2650
Duke Free Electron Laser Laboratory

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System