Experimental Physics and
Industrial Control System

[email protected] (Tim Mooney) · Thu, 27 Aug 1998 12:31:05 -0500

re...

> I'm using Epics v3.12.  I added scan rates of .05 second (20 Hz), .025
> second (40 Hz), and .016667 second (60 Hz) to the list in choiceGbl.ascii.
> I rebuilt default.dctsdr and found these three rates added to the file.
> The problem is that scanppl informs me that rates of ".025 second" are
> running at ".016667 second".  A dbgf "record.SCAN" does return the correct
> value of ".025 second".  A logic analyzer says that the scans are occuring
> every 16.7 milliseconds.  The scanPeriod task that these records are in has
> a priority of 51, the second highest priority.
> 
> I did another test where I removed the 60 Hz entry from choiceGbl.ascii and
> saw the same thing.
> 
> I think the records are being processed by the correct scanPeriod task at
> the wrong period.
> 
> Any insight is greatly appreciated.

You can't run at 40 Hz.  Scan rates are restricted to 60/N Hz, where N is an
integer, because scan tasks are driven by a 60-Hz clock.  (Actually, the clock
could run at something other than 60 Hz, in which case you'd be restricted to
sysClkRateGet()/N.)

Tim Mooney

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System