Experimental Physics and
Industrial Control System

"Konrad, Martin via Tech-talk" <tech-talk at aps.anl.gov> · Thu, 16 Jul 2020 16:00:22 +0000

Hi Christian,
At first sight it might sound like a bad idea to poll devices
periodically: If the values are used rarely this means a lot of
unnecessary communication to the device. However, there are a few points
to keep in mind:

- Every once in a while a PV might draw a lot of attention. If you're
talking to the device for each client that requests the data you might
overwhelm a device with a slow interface or controller in the moment you
need it the most. If you're polling load is always the same.

- Every once in a while devices fail and stop talking. I usually want to
know right away (alarm). If you aren't polling the device how do you know?

- Polling only affects the connection between the IOC and the device.
Generally no Channel Access updates are posted if the value hasn't
changed (or within the MDEL). This usually keeps overall traffic on the
network reasonably low.

-Martin

-- 
Martin Konrad
Facility for Rare Isotope Beams
Michigan State University
640 South Shaw Lane
East Lansing, MI 48824-1321, USA
Tel. 517-908-7253
Email: konrad at frib.msu.edu

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System