bdossantos
Member
Need some assistance. I am testing out a heart beat code and I want to fault the processor so I can check from the SCADA system that the PLC is Faulted and Alarms me. Thank you.
Faulting a AB L33 PLC
- Thread starter bdossantos
- Start date
Ken Moore
Lifetime Supporting Member
Enter a negative value into the preset of a timer. Worked on older CLX platform, have not tried it in a few years.
bdossantos
Member
OP
thank you
jaden
Member
Try a math function that divides an integer by zero.
Oh good one. Could even add a module that doesn't exist and then check the box to fault.
Ken Roach
Lifetime Supporting Member + Moderator
Divide by zero and a negative timer preset are Minor faults in ControlLogix.
But an out-of-bounds pointer in an Array tag index, like MyArray[100] in an array whose elements are [0] through [99], will definitely Major Fault the CPU.
But an out-of-bounds pointer in an Array tag index, like MyArray[100] in an array whose elements are [0] through [99], will definitely Major Fault the CPU.
dmroeder
Lifetime Supporting Member
If you put a negative number in a timer preset and make it true, it will major fault the controller.
Ken Moore
Lifetime Supporting Member
That's what I have done it the past to check fault routines.
Ken Roach
Lifetime Supporting Member + Moderator
Thanks for that clarification about the Timer with a negative preset.
Just moving the negative integer into the Timer's .PRE does not fault the controller, but executing the Timer with a negative .PRE value does.
The out-of-range array pointer is the one that usually catches me in the wild.
Just moving the negative integer into the Timer's .PRE does not fault the controller, but executing the Timer with a negative .PRE value does.
The out-of-range array pointer is the one that usually catches me in the wild.
JaxGTO
Member
I do work in a plant that has over 1000 PLCs all on the same Ethernet. So we use code that on first scan gets the IP address from the Ethernet module and if it doesn't match what the program has as a setpoint, it jumps backwards to fault the PLC.
I am pretty certain that this is not always true - if the array is part of a UDT-scoped tag, and there is something after the array in the UDT, then the "out-of-bounds" crash doesn't work.
Indexed instructions simply check that the destination address calculated is consistent with the tag size, meaning the UDT tag, not the array "member".
Tim Ganz
Member
Could you share a sample of that? We have the same issue as many of the lines are very similar but not exactly the same and sometimes people download the wrong program to the wrong controller and it's close enough that most times it works until we find 1 or 2 small operations are not working and by then sometimes we have ran a lot of bad production that has to be scrapped.
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