DHRIO Receive System Fault From SLC 5

I've encountered a situation where the SLC 5 connected to a Compact Logic via DHRIO does not send the Compact Logix a fault notification if the system (SLC 5) faults out. The reason being, the RIO card inside the SLC 5 rack is still communicating just fine with the DHRIO (in the compact logix rack), however, the SLC 5 has a fault in the processor (S:...bit) but I do not know how to let the compact logix know that.

Currently, I can only detect if there is a communication fault between the DHRIO and the RIO in the SLC 5.

Does anyone know of a solution?

OK this doesn't make since to me. What PLCs do you have and how are they connected? There are several SLC that can talk on RIO. I haven't seen a DHRIO card for a compactLogix. I have seen them for a ControlLogix.

How is the network setup? Is the SLC using a master or a slave card? I think the slave was a DM card.

I agree with Jeff that you are likely using a ControlLogix and a 1756-DHRIO module, with a 1747-DCM or similar module in the SLC-500 chassis. You had a recent thread with this architecture (with a MEDAR variant of the DCM).

This architecture doesn't include any mechanism for determining the runtime status of the SLC-500 controller.

You could "roll your own" very simply by using part of the Output memory as a watchdog; if it doesn't change within a certain period of time, your ControlLogix program can consider the SLC-500 program to be faulted or stopped.

Ken Roach said:

I agree with Jeff that you are likely using a ControlLogix and a 1756-DHRIO module, with a 1747-DCM or similar module in the SLC-500 chassis. You had a recent thread with this architecture (with a MEDAR variant of the DCM).

This architecture doesn't include any mechanism for determining the runtime status of the SLC-500 controller.

You could "roll your own" very simply by using part of the Output memory as a watchdog; if it doesn't change within a certain period of time, your ControlLogix program can consider the SLC-500 program to be faulted or stopped.

Click to expand...

I've never had to create a watch dog but have heard the name several times.
Could I use just standard bits on the SLC-500 side to create my watch dog logic, or are there special bits I need to use to properly create a watch dog for the program?

Since it is very hard to even get this rare processor fault, I want to be sure that the logic works.