ControLogix Produced Messages

deadgecko

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Join Date
Oct 2007
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Cincinnati, Ohio
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Does anyone know of a way to monitor the number of consumers of a ControLogix produced tag?

I have an application with over 30 CNet nodes connected to a supervisory ControLogix processor (mixture of PLC-5's, ControLogix processors). The supervisor produces a tag that used for line control and synchronization and I would like to monitor the number of devices that consume this tag. I know what the value should be and want to verfiy that all nodes are receiving the tag. If the number of consumers is not equal to the expected value a stop is created and the process is stopped due to a CNet Comm Fault.

The supervisor was recently upgraded to ControLogix from a PLC-5. Before the update I could monitor the status words for the produced tag (message) to see how many devices were consuming the tag.

Now with the produced tag being created in RSLogix 5000, I do not have the option of monitoring the status words for the tag. I have been using a GSV to check the Entry Status for each of the devices, but recently one of the PLC-5 consumers was reloaded and the scheduled consumed message was not entered. For some reason the GSV did not catch the fact that the message was not being consumed. The device in question was unaware of the process starting and did not apply the required component.
 
One thing is a produced tag an other is a message. When a tag is produced by a clx ( compact logix ) this is consumed by others clx or compact logix.

A produced tag has no condition and is sent to receivers permanently, a message can have a condition and when that condition is true then the message is sent.

if you´re sending messages you can write some ladder code on reciver to reply when they recive a message.

hope this will help
 
That's a neat mechanism. You were using the second Word in the ControlNet Connection Status data entry on the PLC-5's, right ?

I've never investigated this before, and I thought I'd been through about everything with ControlNet.

I know that RA has discussed adding Produced/Consumed Tag status elements to the Controller scope tag database when you create a Produced Tag. I don't know if the number of connected consumers is planned to be part of that.

When I get a chance I'll dig and see if I can find a CIP object to which you can send a message to get this data.
 
I guess I should clarify a little. It is a little confusing when ControLogix processors are communicating with PLC-5's. The terminoligy is different.

In a PLC-5 only enviorment, there are scheduled and unscheduled messages (there are no produced/consumed tags). Scheduled messages are setup inside RSNetWorx and then the CNet config is downloaded to the network. You must setup up the produced message inside the producers scanlist config and also setup the corresponding consumed message inside the consumers scanlist using RSNetWorx. For each entry in the scanlist there are 3 status words created for message. For a produced message, one of the status words contains the number of consumers of that message.Unscheduled messages are setup inside the PLC logic using a MSG instruction.

In a CLX only enviorment produced/consumed tags are setup inside RSLogix 5000 individually for each processor, be it producer or consumer. There is no need for RSNetWorx and there are no status words created for these tags.

In my application the supervisor CLX produces a tag that needs to be consumed by multiple PLC-5's and CLX processors. To do this you must schedule a receive message inside of RSNetWorx. This is different than using a MSG instruction that is an unscheduled message. You must also setup the consumed tag inside the CLX processor.

What I need to do is monitor the number of consumers to verify that the produced tag has been seen by all devices. I would think that using a GSV for the Entry Status of the CNB module in the supervior rack could tell me how many devices are consuming the produced tag, but have been unable to confirm from any of the manuals for the CNB or ControlNet.
 
Ken,

That is correct. The second status word contains the number of consumers of that message. To bad it is only good when using PLC-5 to PLC-5 scheduled messages.
We also used bit 8 of the first status word for invalid data and bit 9 for connection errors. The third status word would tell you if the consumer processor was in RUN mode.

I could tell you horror stories of all the issues I have seen with CNet. My local Rockwell rep hates to take my calls, because I always seem to have an issue that no one has ever seen before. There have even been a few firmware revisions due to issues I have found. Don't even get me started on 1394 GMC issues.
 
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