Ron Beaufort
Lifetime Supporting Member
I just took a QUICK look at the "power up" handler you posted ...
first thoughts: I doubt that the "unconditional" ONS rung will work the way you have it ...
secret handshake: with a ControlLogix (and incidentally with a PLC-5)
each time the processor goes into the Run mode, a PRESCAN operation takes place ... during the prescan, all ONS instructions have their "status bits" set to a ONE condition ... this is done (for better or for worse) to prevent "false triggering" when the system first starts up ... (note that this rule is slightly different for MicroLogix and SLC systems) ...
so ...
regardless of whether the "fault handler" itself ever gets executed or not, I don't think you're going to get the desired operation out of that ONS rung ...
hint: you should be able to use the "scan counter" idea I posted earlier to check out the operation of an "unconditional" ONS rung at start up ... specifically, put that rung in a "standard" (executed) routine file and switch the processor from Program mode to Run mode a couple of times ... you won't need a battery for that test ... (this will trigger a PRESCAN operation) ... notice that the unconditional ONS will NOT fire the way you might expect it to when the processor first goes into the Run mode ...
I'll try to take a closer look at your posted programs later today (or tonight) if I get some free time ...
first thoughts: I doubt that the "unconditional" ONS rung will work the way you have it ...
secret handshake: with a ControlLogix (and incidentally with a PLC-5)
each time the processor goes into the Run mode, a PRESCAN operation takes place ... during the prescan, all ONS instructions have their "status bits" set to a ONE condition ... this is done (for better or for worse) to prevent "false triggering" when the system first starts up ... (note that this rule is slightly different for MicroLogix and SLC systems) ...
so ...
regardless of whether the "fault handler" itself ever gets executed or not, I don't think you're going to get the desired operation out of that ONS rung ...
hint: you should be able to use the "scan counter" idea I posted earlier to check out the operation of an "unconditional" ONS rung at start up ... specifically, put that rung in a "standard" (executed) routine file and switch the processor from Program mode to Run mode a couple of times ... you won't need a battery for that test ... (this will trigger a PRESCAN operation) ... notice that the unconditional ONS will NOT fire the way you might expect it to when the processor first goes into the Run mode ...
I'll try to take a closer look at your posted programs later today (or tonight) if I get some free time ...