S7 315-2 DP with Bus Fault and System Fault despite empty program

RMA

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Sep 2004
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North of Hamburg, Germany
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We've got a 315-2 DP with MMC which behaving a bit peculiarly. Despite having loaded an empty program and setting up the busses in Netpro to reflect the currently available devices the BF Led is on steady and the SF Led is blinking.

More curious is that in the diagnostic buffer, the CPU is reported as having gone from STOP to RUN with no faults. Despite that, the little fault symbol beside the CPU icon is showing a fault.

Anybody seen anything like this before and if so is there a solution?

Or are our increasing suspicions that the CPU is faulty, the most likely cause of this state of affairs, correct?
 
I had something similar, and we thought the MMC had gone bad. Replaced the MMC with a blank one and the processor came back up. Put the suspected bad one in another CPU just to make sure, and that one came up OK too. So don't know what originally caused the problem but swapping MMC definitely seemed to help. Maybe it wasn't seated well to start with. Diagnostic buffer was no help in this case.


I don't know what the consequences of having an empty OB1 with a networked hardware configuration would be. I wouldn't think that would cause any problems.
 
Similar story for me, got a 315 out of the box (only the third one I've ever used) and it didn't want to work the first time I downloaded a h/w config. After various resets and downloading alternate h/w configs, it eventually worked - I think you'll find its not faulty. (Anyone ever had a faulty one out of the box ?)
 
we get the occasional problem with S7 400's, the PLC fails on hardware, just compiling and downloading the profile again and hey presto, all'd fine.
 
Thanks for the suggestions, the customer beat me to it this morning and was in the process of rebuilding the program from scratch as I arrived. Recreating the structure in HW-Config and copying in the program blocks from the original program, downloaded and, hey presto, everything's OK again. Evidently something in the system data had got screwed up - at least we didn't need to wait for a new CPU to be delivered, we're supposed to be commissioning next week!
 
If you're making download from NetPro, Step7 doesn't download all system data to the CPU. If you want download all system data of you PLC you should do this from block folder (for new CPU's and CP's), or first download hardware from HW Config and then connections from NetPro.
 
Culprit found!

The culprit appears to have been a corrupted GSD file for the Burner controller.

Reloading the file and then rebuilding the system cured everything. How the corruption occurred in the first place is another matter altogether.
 

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