Experimental Physics and
Industrial Control System

"Steven M. Hartman" <[email protected]> · Tue, 27 Sep 2011 17:32:24 -0400

Di Maio Franck wrote:

But I also wonder if others with similar requirements (predictable traffic with PLC) are using a dedicated network interface to separate the PLC traffic from CA.

Hello Franck--

How predictable do you require, and how fast are you expecting for

PLC to EPICS communications? For SNS, we are not relying on tight

timing requirements between IOC and PLC (typically ~1 second is

adequate) and we can tolerate a long timeout (several seconds).

Anything with lower tolerance is handled within the PLC (or within

the IOC). With this expectation, we do not see anything like your

flicker, and when we have seen problems, it has generally been

traced to a buggy firmware version on the PLC or bad hardware (e.g.

damaged network cable). The SNS network is relatively flat and has

lots of traffic. A dedicated network may be beneficial, but I think

in our case, the inefficient network protocol to the AB PLCs is more

of a limitation then the network capacity. I don't have experience

with the S7 PLCs for comparison.

Regards,
--
Steven Hartman
[email protected]

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System