Control logix Network

I am working on control logix processor with no of remote rack.
ON control net with CNB module.

i required if nay one NODE is fail to communicate PLC delare a alarm on HMI, but how to i catch the particular NODE is failed

use a handshake

Handshake? I'll assume you mean, dedicate a digital output, and a digital input, with the output wired to the input, on the remote rack, and continuously toggle the output state. Then monitoring the input would show if comms exist to the rack.

It would probably be better to use GSV to get information about the state of the CNB Bridge in the main rack. Look in the ONLINE MANUALS for ControlLogix, General instructions, Input/Output GSV / Module.

Re-reading the exact wording, I think they are referring to the status of the CNB module? In that case, either use a GSV or a CIP message.

Attached is an example used for detecting Ethernet IO, which will also work for ControlNet. Place code in a periodic task (typically I use 100ms).

Also, watch out for executing the GSV to rapidly. I believe there are some tech notes that disuss problems related to too many / too fast executions of GSV statements.

The comments at the top of the ladder are directly from the online help and the code was made neater than my original from help of Ken Roach.

Darren