Experimental Physics and
Industrial Control System

John Dobbins <[email protected]> · Mon, 03 Dec 2007 18:17:19 -0500

I am working on device support for a device which is volatile in the sense that
it can change in ways other than through the EPICS IOC. For inputs this is not a
problem, periodically scanned input records will get the current value. For
output records it is not obvious how to deal with this. I would like the output
values displayed on the operator screen to be correct even when they are changed
via means external to EPICS.
Ether_IP, the device support for Allen-Bradley hardware, is an example of a
device support that does this. The device driver periodically reads from
hardware the values corresponding to EPICS output records and executes a
callback to update the output record. In this way the EPICS output record has
the correct value even if someone changes a PLC tag via the vendor software RSLogix.
Is there another example of a device support which does this?
John Dobbins
LEPP
Cornell University

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System