Micrologix 1200 ERROR

[Ron Beaufort]

here's what I'm finding that looks "fishy" ... specifically, it seems to have faulted INSTANTLY (on the First Pass) - and it looks like the Status File has been set to Always Load from a Memory Module - and the memory module doesn't seem to actually be present ...

first guess ... someone inadvertently changed the program to require a memory module - and didn't provide the module ... but I'm not betting more than pocket change on this one ... but it sure does look "fishy" from where I'm sitting ...

EDIT: as long as it is SAFE to do so - you might try changing bit S:1/11 (shown as a ONE below) to a ZERO and see if the thing will start up OK ...

.

 

[daba]

I'd be suspecting those DIV instructions in File 3.

In all cases for F8:0, F8:1, and F8:2, the "trap" rung that prevents it going to zero, is after those table values are used.

If the HMI writes a 0.0 into those addresses, then the DIV instructions will all overflow.

I would swap the rung order around, put the trap rungs above the calculation rungs.

I have been through the entire program, the overflows would definitely be caused if F8:0, 1, or 2 are zero when the processor starts scanning.

In file 3, I recommend swapping rungs 0/1, rungs 2/3, and rungs 4/5. This will place the "traps" in front of the places where those values are used as divisors, eliminating any "Division by Zero" overflows.

I would also recommend that you put a single rung as the last rung of file 2, with an OTU of S:5/0, the Overflow Trap

 

[Ron Beaufort]

if this is a "faulted" copy of the program (as reported) - then I've got a hunch that the S:5/0 overflow trap bit is not an issue ... that bit is not set to ONE in this copy ...

 

[daba]

here's what I'm finding that looks "fishy" ... specifically, it seems to have faulted INSTANTLY (on the First Pass) - and it looks like the Status File has been set to Always Load from a Memory Module - and the memory module doesn't seem to actually be present ...

first guess ... someone inadvertently changed the program to require a memory module - and didn't provide the module ... but I'm not betting more than pocket change on this one ... but it sure does look "fishy" from where I'm sitting ...

EDIT: as long as it is SAFE to do so - you might try changing bit S:1/11 (shown as a ONE below) to a ZERO and see if the thing will start up OK ...

.

Good call Ron... But i would still correct the rung orders as indicated ....

Also these from the Help...

"When S:1/10 is set in the status file of the user program in RAM memory, the memory module must be installed at all times to enter REM Run or REM Test modes."

and

"When S:1/11 is also set in the status file of the user program in RAM, the memory module must be installed at all times to enter the REM Run or REM Test modes"

 

[Whiskey007]

Before i forget i just want to thank all of you for your responses so far........ really appreciate !

I have changed the S1/11 setting to 0 and the same thing happens fault appears upon going to run mode.

Just throwing out some more details of the history of the problem, these three units were working fine on friday then on Ssaturday there was an alarm shutdown on one unit which in turn created high pressure alarms on the other units as the feed water is running manually and it tripped the over pressure switches. We have had these alarms in the past but with a reset everything was good to go again.

If there was a glitch with the PLC program in one unit why would all three come up with the same exact error problem the same time ? As i said earlier these are all linked to a SLC 500 Allen Bradley for communication, that being common to all of them is it possible the problem could be occuring here ..........only asking remember i do not know.

 

[Ron Beaufort]

I have changed the S1/11 setting to 0 and the same thing happens fault appears upon going to run mode.

after the fault - was the S:1/11 bit STILL set to ZERO - or was it somehow mysteriously changed back to a ONE status? ... (thought: maybe the change didn't actually get downloaded into the processor) ...

these are all linked to a SLC 500 Allen Bradley .. is it possible the problem could be occuring here?

that could be possible ... can you post the program file for the SLC 500 also? ... we'd be happy to take a look at it ...

 

[Whiskey007]

The S1/11 bit remains at 0 even after the fault so i would assume it accepted the download ...

Will try to attach the other programs shortly

 

[Whiskey007]

Here is the program file for the SLC 500.

Sorry attached the wrong file will try again.

 

[Ron Beaufort]

this appears to be just another copy of what you've already posted ... are you getting these files as "uploads" from the processors - or just lifting them from a computer's hard drive? ...

let's make sure that we're dealing with current information ...

EDIT: I see that you realized your posting error ...

the BIG question so far is how on earth did your 1200 work at all - with those settings that I highlighted above? ... we don't doubt what you're telling us - but we need to make certain that we're all working from the same page ...

 

[Whiskey007]

I totally understand where you are coming from so I will verify the files tommorow once i am back infront of the unit and resend as necassary.

 

[Whiskey007]

Ron you were absolutly correct i sent the program file from the computers hard drive. I have attached a new file uploaded from the PLC with the fault triggered and also one without the fault triggered. So before i make any changes to the file if one of you could take a look at these new files and see if anything stands out as out of the ordinary...............thanks !

 

[Ron Beaufort]

neither of the last two programs that you posted were in the faulted state when you saved the files ...

but at least the weird "memory module" settings are gone in these copies ...

 

[Whiskey007]

We downloaded a copy of the program that we had saved on a memory stick from when the unit was first set up and what do you know it's working fine again so I have one last question could something such as a power surge, electrical noise etc corrupt the program file that the PLC was running , is that possible at all or would someone have physically had to change it ?

 

[Ron Beaufort]

if you'll post the "working" program file, we'll be glad to compare it with the others that you've already posted ... maybe we can spot the differences (if any) that could account for the symptoms that you're reporting ...

right now we're just having to guess - same as you ...

we're glad that you've got it working ... we hope that it doesn't come back to haunt you ...