RsLogix Studio HowTo clear Watchdog major fault correctly

Hi,

I'm developing a routine to detect and clear a watchdog major fault in a ContolLogix PLC. The software has three tasks and six programs.

According to the "Logix 5000 Controllers Major, Minor, and I/O Faults - Programming Manual" I've created a Controller Fault Handler (for major foult type =6, code = 1 => watchdog) in order to detect and clear the major fault.

The example of the manual uses the keyword THIS in order to address the program object of the GSV/SSV instructions accessing to the fault record of the current program.

I've done the same (see attachment) but my fault handler Routine is part og the FaultHandlerProgram in the ControllerFaultHandler folder so, which PROGRAM is THIS if a watchdog major fault occurs? Is this the correct way or I've to specify the name of each program?

Thanks a lot

Carlo L.

Yeah, I don't think you can use "This" with the Fault handler in this way. Maybe you can, but I wouldn't.

Instead, program a GSV/SSV for each Program. Assign a different internal fault bit and different fault tag for each one so you will know which program the controller was scanning when the fault occurred. Then you can use that bit to trigger the specific SSV.

Keep in mind, if you clear the fault, it will return you back to where you were when the fault occurred. If the controller was caught in a loop, then you are right back in that same loop.

Let's say you are caught in a loop. If you have a watchdog fault, clear the fault, and return to where you were and have another watchdog fault without ever finishing the scan, it will fault again and it will not clear it the second time.

OG

Thanks.

When you say "program a GSV/SSV for each Program"
you mean that I've to program a fault handler as a program routine or a couple of GSV/SSV instruction for each program?

Thanks

Carlo L.

Looks like I was mistaken. They do explicitly say that for a Watchdog fault you need to do it the way you have done it.

A watchdog fault is essentially happening outside of any individual program. It is occurring at the task level. THIS in this case is simply the fault handler program. I don't think the program is important here. Might have to test this out myself.

OG