AB PLC 2 Communication Ports and Protocol

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Thread Starter

Brian Tober

I am trying to talk to a PLC 2 that has one port, the port is being used by a display panel, I am trying to use Citect as the HMI and have a KT card installed but PLC 2 uses some old protocal that I assume has to be converted to DH+. AB wants to charge me for legacy support for tech advice on this PLC. Any advice would be greatly appreciated.
 
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Jerry Miille

Brian, our first product, the Comm-Troller was designed to talk to a PLC 2 and I have some experience with the communication requirements. Please contact me at [email protected] and I will try to help you.

Thanks,

Jerry Miille
 
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Eric M. Klintworth

The PLC 2 was designed (in the late 1970's) to talk to a single dumb terminal connected directly to its front port. The Allen-Bradley 1785-KA3 module is a PLC-2 to Data Highway Plus adaptor module. Take a look at the manual for that module at:
<http://www.ab.com/manuals/cn/1785653.pdf>
That should give you a good idea of the nightmare you would be getting in to trying to get two devices (display and HMI) to talk to the PLC-2.

Advice? Consider a different approach (there are several options). Communicating with the PLC-2 is sort of a pain to start with, but is a real "adventure" if the front port is already "taken". You will end up replacing the "display panel" and redoing any programming in the PLC-2
that supports it, plus any logic in the PLC-2 that will be necessary to talk to the Citect. And have you ever programmed a PLC-2? Don't let
anyone tell you its "just like a PLC-5"--it isn't!

Ken Roach, others, agree?

I didn't believe them at first when I was told the first PLC-2/30 I ever programmed had magnetic core memory, but it was true. The PLC-2 is not
exactly latest and greatest...

Eric M. Klintworth, PE
Columbus, Ohio
 
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Michael Griffin

<clip>
>I didn't believe them at first when I was told the first PLC-2/30 I ever
>programmed had magnetic core memory, but it was true. The PLC-2 is not
>exactly latest and greatest...
<clip>
And what was even more interesting, it didn't use a micro-processor to run your ladder program. There were 4 AMD 2900 bit slice processors which AB used to construct their own CPU (just like a mini-computer).


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Michael Griffin
London, Ont. Canada
[email protected]
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