Fault Handling

Hello all,

New member to the forum here. I have a question about fault handlers that I'm not too clear about - may seem pretty basic but I can't find an answer anywhere.

Why is it that GSV's for major fault detection must be placed in fault handler routines rather than main routines? What happens if they are executed on every scan as they would be in a main routine?

Thank you all!

So a GSV can be located anywhere. And we will assume Rockwell PLCs since the GSV is an instruction in the Logix 5000 family. We will also assume you are using the GSV to capture fault information.

However, the idea is that as soon as a controller detects a fault it will immediately jump to a fault handler/routine. If there is no fault handler, the controller immediately shuts down.

By putting the GSV into the fault routine you can capture information on what caused the fault. If the GSV was in the normal logic (main routine) it would not have captured the fault data.

OG

Oh, and the GSV is not DETECTING a major fault. It is used to capture data when a fault does occur.

The controller itself detects the major fault and calls the fault handler.

OG

Thank you for the reply Operaghost! Very informative.