Experimental Physics and
Industrial Control System

Kay-Uwe Kasemir <[email protected]> · Wed, 23 Jul 2003 12:02:33 -0600

At 11:27 7/23/2003, Paul M. Morris wrote:
>So....the missing link is a way to speak to our A-B PLCs.  We [believe we] want to communicate over Ethernet between the IOC and A-B PLC.
>1) Does anyone have similar systems running in this configuration?    [I was told SNS did this, but am not certain.]
>    --Could you recommend hardware?
>    --Would you share available drivers?

For SNS, we picked the A-B ControlLogix PLC
which can be accessed via EtherNet/IP.

That's ethernet, using TCP/IP. The "IP" in EtherNet/IP isn't "Internet Protocol"
but "Industrial Protocol", at one point in time called "ControlNet over Ethernet",
which is wrapping CIP (Control & Information Protocol) messages into TCP.

www.odva.org somewhere has a description of all this.
With that, you can write a driver that reads the
serial number out of the ControlLogix PLC's network module.

After Allen Bradley published their special
CIP service codes for reading and writing ControlLogix tags,
we implemented an EPICS driver & device layer.
More info on that is here:
http://arXiv.org/abs/cs.NI/0110065
Stephanie Allison (SLAC) recently ported it to EPICS R3.14.

SNS uses it in _many_ places,
Los Alamos LANSCE is beginning to use it,
and SLAC, I believe, has a few PLCs.

Note that even though "EtherNet/IP" is sold as a great
and open protocol for everything,
at least in the ControlLogix case it turned out that
EtherNet/IP is useless without the ControlLogix
specific service codes, so the EPICS driver I'm talking
about is only for A-B ControlLogix PLCs.
Porting it to other "EtherNet/IP" devices would be
very much like starting from scratch.

Thanks,
-Kay

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System