DeviceNet (Ken Roach)

Definately in a bind here.

I have a DeviceNet network, using 1769 SDN and MicroLogix 1500's,
7 Nodes. I need 6 nodes to explicit message to the remaining node. Only 4 of them work, the explicit message fails in the last two nodes to join the network. I can unplug one of the good working nodes and then one of the nodes that was failing begins to work. I plug in the previously working node, and the messaging fails.

I don't think it is my network cable. I have the shield grounded, the V- is tied to to ground. I have a devicenet power supply. My network is only 100 ft. I am communicating at 125Kb. My network ohm's out at 60 ohms. My Can H and Can L are operating within spec. Can H is swinging between 2.5V and 4V, Can L is swinging between 1.5V and 2.5V.

I am looking at the network on my scope, it is definately not a bandwidth issue or noise issue.

I have tried using different nodes. nothing changes. I have completely rebuilt the network new cable different PLC's different 1769 SDN's, different devicenet power supply.

Note: The explicit message only fails if I try and send it to the same node every other node is trying to talk to. If I configure the message to communicate with a different node the message does not fail.

My problem is getting more then 4 nodes to expicit message to one????

This is not cool.....Gonna have to get AB in here, unless someone may shed some light on this situation.

Thomas

All the nodes are MicroLogix 1500 1764-LRP's with 1769-SDN's, right ? I've done some limited peer-to-peer with these, but never run into a maximum connections problem.

Describe more about what data you're sending to and from each node. This sounds like it might be accomplished more easily by using the 1769-SDN's in Slave Mode.

What is the exact explicit message Class/Instance/Attribute and what is the error code ?

Ken Roach said:

.....This sounds like it might be accomplished more easily by using the 1769-SDN's in Slave Mode.....

Click to expand...

I don't have a reference but I believe you're right; IIRC it will only work and be succesfull in slave mode.

Ok....I was under the impression that if you are not using the I/O inside the scanner...There is no need for a Master/slave definition.(even if I do define a master slave connection and map a couple of words to and from each node, the messages from the last two nodes fail.)

I do need that functionality, but I am trying to simplify my network as much as possible.


I am using 500CPU writes.
Communicating throught the expansion comms port.

Because I am using 500CPU writes and I am communicating with another Micrologix I don't need to define class/instance/attribute.(pretty sure)

I am sending 13 words of data. The data I am sending is all zero's.(just wanna see the message not fail). If a the message fails I am turning on a output(I can hear a message and see a message fail). I am sending 1 message from each unit every 2 seconds.

Thomas

More info....sry I didn't answer your first question...yes every node is a 1769 SDN connnected to a MicroLogix 1500 LRP.

The error I get is e0...I recieve the error less then 100ms after the message is enabled.

Phone support told me that is error from the 1769 SDN, and that it means the message was not even sent.

In the manual it says to look at sub element 22 for more details but I don't where to find that sub element.

Thomas

The slave mode I/O connection is not required for the SLC-style encapsulated messages to work. I was just saying that you could use the slave-mode connection *instead* of sending MSG commands.

Hey....so I talked to the AB tech around here and he told me there was know tech note regarding a limitation on the micrologix LRP explicit message maximum. He told me the engineers were looking at it and he would get back to me...that was a couple of days ago....From everything that i tested, I believe there is a limitations on how many nodes can explicit message to one.


I got around this problem by doing all the comm in my host PLC. Instead of having all the nodes write to my Host. I changed it around and got the host to read out of every unit.

Wish I would have known about that limitation. I spent three days trouble shooting my comms and redoing everything becuase it should have done what I was trying to do.

Oh well.....on to the next problem.

Thomas