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| <== Date ==> | <== Thread ==> |
|---|
| Subject: | Re: [S7plc EPICS driver] REAL type record jumps to zero |
| From: | "Steven M. Hartman" <[email protected]> |
| To: | Di Maio Franck <[email protected]> |
| Cc: | "[email protected]" <[email protected]> |
| Date: | 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]