peer-to-peer messaging between two ControlLogix PLC's


Thread Starter


Hello everybody,

I have two PLC’s ControlLogix and need to exchange some data peer-to-peer.
The data (about ten words from plc 1 to plc 2 and ten vice-versa) consist of time-critical data such as interlocks and setpoints, therefore I cannot/do not want to use Ethernet/IP explicit messages. On the other hand those data do not require ControlNet determinism. Also I do not want a ControlNet link just for this purpose cause each of the two PLC’s has already the following communication modules:
- Ethernet/IP for remote I/O purposes
- Ethernet/IP for Scada purposes
- DeviceNet for drives communication

How can I exchange those data at a speed implicit-messages-like, exploiting the above networks?

How can I exchange those data at a speed implicit-messages-like, exploiting the above communication modules ?

You're going to use Produced / Consumed Tags, which is one of the most powerful and prominent features of the ControlLogix. All you have to do to exchange such tags is to configure a tag as a Producer in one Logix, and to configure another tag as the Consumer in another Logix (you also have to configure the Producing Logix controller in the I/O tree of the Consuming Logix controller.).

Produced/Consumed tags are exchanged at the Consumer's Requested Packet Interval (RPI) using the same UDP/IP mechanisms as I/O on EtherNet/IP protocol.

This feature is well documented in the ControlLogix literature.

You can use Producer-Consumer tags for transmitting data between two ControlLogix Processors. You don't need to write separate Message Instructions. You can define data transmite rate in Consumer CLX at RPI in mSec(Request Packet Interval)

For details about using Producer-Consumer tags, refer ControlLogix User Manual (Chapter-5: Communication with Another Controller over an Ethernet/IP Network) which is included in the Online Manuals in RSLogix5000 package. (Help-Online Manuals - ControlLogix Manuals - ControlLogix System User Manual)

OK. Hope this will do.

Vijay PNG