Help needed! Remote messaging between two SLC 5/04's via DHRIO modules.

gary steigh

Member
Join Date
Oct 2002
Location
lomita, calif
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7
I'm trying to send remote messages from a SLC 5/04 on one network to another SLC 5/04 another network using ControlLogix DHRIO modules. I communicate with the ControlLogix chassis via a 1756 ENET card. I can do everything except send a remote message. I've went through all the Rockwell Knowledgebase's concerning this application, but cannot resolve this messaging issue. The error code that I always get is d0, with the comment that no ip address has beed configured for the network. I've made sure that the local bridge address is correct, that the bridge link ID is correct and that the remote station address is correct.

What am I doing wrong??????????

Sincerely, Gary Steigh
 
If your DHRIO routing table is correct, and your Channel 1 configuration is correct on both controllers, and your MSG instruction configuration is correct... then the MSG would work.

So one of those has to be incorrect, don't you presume ?

Post all those items (check in the Practice Posting forum if you need help posting graphics clips), especially the Routing Table from the DHRIO, and maybe somebody will be able to identify a setting that needs to be changed.

In my experience, the setting that many users overlook is the "Link ID" setting for Channel 1 of both SLC's; to do inter-DH+ messaging, each local DH+ network must have the same Link ID setting on all the DH+ nodes.
 
Ken are you refering to the channel configuration, general tab, channel 1, passthru link ID on each slc on the network?
 
Yes, that's the "passthrough Link ID" number I'm talking about. I see that Gary posted a screen capture of one of his SLC-5/04 controller configurations over on the Practice Posting forum, so he's probably working on this.

I can set this up with a pair of SLC-5/04's and a gateway in my office on Monday (the only day I'm in town this week) but Gary hasn't fed back anything so I'm not sure that it would help him to post an example of a working message (which he's already seen in the Help files).

According to his location flag he's under United Nations interdiction anyhow.
 
Ken, I apologize for not getting back to this forum sooner. Your insight into the passthru link ID was the solution to my problem. From then on its been very busy. Thanks again for the help.
 
Last edited:
I'm glad to hear that you got it working, Gary.

For those of you playing along at home, a little exposition on DH+ "Remote Link Addressing".

When a message needs to transit between separate DH+ networks, the mechanism used to differentiate between the DH+ networks is the "Link ID".

The nomenclature is a little obscure; nimodo pointed out that it's labeled the "Passthru Link ID" in RSLogix 500 Channel 1 Configuration. "Link" is just a word left over from the distant past when DH+ was called "Peer Communication Link" (PCL). "Subnet", "Segment", and "Network Number" all have different connotations, so "Link ID" is the term we'll use.

The most popular way to connect multiple DH+ networks together today is a little gem called the 1756-DHRIO. It is a two-port module that fits in a ControlLogix chassis and one of it's primary duties is to bridge DH+ messages.

If you have just one 1756-DHRIO that is running both channels as DH+, this is a relatively simple task. In the "Routing Table" configuration for the 1756-DHRIO (configured using an applet within RSLinx) you configure a Link ID for each DH+ Channel on the module. The easiest settings are Link ID 2 for Channel A, and Link ID 3 for Channel B.

Now you have to go back to all of those DH+ nodes on each separate DH+ network (a.k.a. "link") and configure their Link ID to match the DHRIO channel to which they are attached.

A "Remote Message" from a controller on one network to a controller on the other network needs the Remote Link ID and the Remote Node Number. Once the message arrives as the DHRIO module, it routes it to the channel that matches the Remote Link ID in the message.

This is a simplified example; the DHRIO can do a lot more. For example, you can define a route that goes through a complex Rockwell CIP network path (over Ethernet, over ControlNet, through the woods to Grandmother's house, and to another DHRIO) and define a Link ID for that whole path. The DHRIO will encapsulate your Remote DH+ Message (which contains just a destination node and Link ID) and hustle it over that CIP path, with the MSG block in the originating controller being none the wiser.
 

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