AB PLC5 communication

I am trying to establish communication between two Allen Bradley PLC5 plcs on dh+ port(which is a three pin connector).Both of them are having node address 1.Please tell me the steps how to configure both plcs to communicate with each other.what are local and remote messaging?Is it necessary to know about them in this context?Is any software change required?kindly help

Welcome to the Forum !

What is the exact model number of each PLC-5, and which Port number is the DH+ port ?

Most PLC-5 controllers have "Channel 1A" configured by default for DH+ protocol, and Channel 1A's address is set by DIP switches on the controller. You can read about how to set those up in the PLC-5 user manual.

In general, controller-to-controller messaging is considered "Local" DH+ messaging. "Remote" messaging is much more complex and involves multiple DH+ networks that are carefully connected with network bridges.

You can read about DH+ messaging using the MSG instruction in the PLC-5 Instruction Set Reference.

Links to useful documents:

PLC-5 Enhanced and Ethernet Hardware User Manual
http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1785-um012_-ru-p.pdf

PLC-5 Instruction Set Reference
http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1785-rm001_-en-p.pdf

Thanks for replying.The model is PLC5 40C .The DH+ port is 1A.Also connections are made in 1B(remote I/O scanner).Will changing of DH+ address also effect devices in 1B.Will devices connected in 1B loose communication after changing DH+ address?Is any ladder logic like DH messaging need to be incorporated for message exchange?Any changes in processor properties?

Will changing of DH+ address also effect devices in 1B.Will devices connected in 1B loose communication after changing DH+ address?

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No, as Ken stated channel 1A's DH+ address is set by dip switches on the processor. It has no effect on channel 1B.

Will devices connected in 1B loose communication after changing DH+ address?

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No

Is any ladder logic like DH messaging need to be incorporated for message exchange?

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Yes, a message instruction will do this. See the manuals provided by Ken above.

How much data do you want to exchange?

Thanks a lot.This is a great help

sk1984 said:

I am trying to establish communication between two Allen Bradley PLC5 plcs on dh+ port(which is a three pin connector).Both of them are having node address 1.Please tell me the steps how to configure both plcs to communicate with each other.what are local and remote messaging?Is it necessary to know about them in this context?Is any software change required?kindly help

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No-one has mentioned that your two PLCs must have different node addresses...