ControlLogix Devicenet Missing Node Identification

We have a 1756-L55 system, with 2x Devicenet scanners, 1 with 50+ nodes, the other with < 10 nodes.

90% of the time, this system functions ok, but on the reasonably regular occassion some of the nodes drop off the network, either by power failures or other issues.
To assist in debugging this issue in the future, we have thought about adding 'node status' indication to the HMI. What I am not sure of is how to retrieve this information from the scanner.

The scanner itself as a 124 element DINT array configured for Input/Output status monitoring/control.
There is a combination of node types, predominatly being 1791D-16BO modules, with some valve banks as well.

What is the best way to get the status of each node on the network, so that it can be displayed?
It looks like each module has 2x elements allocated, but I am not sure if any bits of the elements provide any status information or not?

Easy option would be to add in an 'always on' input to each node, but I am not sure what is available on each node. Reading the status seems like the better optoin.

Actually it's a lot easier than that.

In addition to the Input and Output Connections, the 1756-DNB has a Status connection of 32 double-words.

It includes a handful of useful status information such as the DeviceFailureRegister, which is a SINT[8] array where each bit represents a node address on DeviceNet. When there's a connection failure, the corresponding bit goes true.

Even more helpful is the DeviceStatus array, which is a SINT[64] array that contains an error code for any broken connection. You'll typically see a fault code 72 here for a powered-down device, or a 77 for a size mismatch.

There's even a 4-byte StatusDisplay array where each byte is the ASCII equivalent to what's on the dot matrix display on the front of the 1756-DNB. If you wanted to echo what's in on the DNB display in an HMI, that would make it easy.

There's also a Diagnostic Faceplate for FactoryTalk View SE/ME in the Samplecode website, that plugs right into the Status connection for the 1756-DNB.

Ken,

That is all excellent information. I overlooked the S register, if I had of looked a bit more I would of found it!

Ken Roach said:

Even more helpful is the DeviceStatus array, which is a SINT[64] array that contains an error code for any broken connection. You'll typically see a fault code 72 here for a powered-down device, or a 77 for a size mismatch.

Click to expand...

In which document would I find the error code explanations? I think I am going to add a table to the SCADA with the status indications, and maybe even the fault codes, so that it will assist the maintenance guys even more!