Hello everyone,

Something strange happened while I was downloading a project on a IM 151-8 PN/DP cpu. Suddenly the connection to the plc drops down. I can't reach the plc anymore through ethernet connection. Looking at the plc I see that the ethernet interface is not working (ports leds are not lit). Furthermore all the leds of the plc are blinking quite fast (it seems like 2Hz) at the same frequency, even the stop led. If I try a memory reset using plc switch MRES it doesn't work (stop led continues to blink). What should I do in this case? I don't even know what situation I'm exactly in. Thank you for your help.

UPDATE

It seems that when all the leds are blinking the cpu is in a so-called "defective state". I managed to exit from it following the procedure "Resetting to the as-delivered state" described at page 156 of the IM 151-8 manual. The problem is that, after this reset, when I plug back in my MMC the cpu requests a memory reset (stop led starts flashing slowly at 0.5 Hz). As soon as I press the cpu switch on MRES position the stop led starts flashing faster and after a while the cpu returns into the "defective state". My best guess is that for some reason the MMC content is faulty and as soon as it gets loaded it blocks the cpu. How can I solve this? I think that I need to format the MMC, is it possible to do it without a Siemens prommer?

hi dan90,

no, you can only format it with a Simatic Prommer.

regards,

Thank you for your answer.

Unfortunately I don't have the prommer for mmc. I managed to get a brand new mmc, when I put it inside and reset the plc restart to work correctly. I tried to load an empty project (only plc and empty ob1) and it gets loaded and runs without problems (just to double check that the problem is not the plc). BUT when I try to load my project after a few seconds the cpu goes into defective state and the load is interrupted. I didn't realize it the first time, but now I'm sure: it loads a few blocks in the plc and then the plc goes into defective state and the loading process is aborted. What can cause such a behaviour? I have recompiled both hardware and software and the software runs fine on the simulator. I'm using Tia Portal V14 SP1 Upd 2. Thank you in advance for your time.

hi dan90,

perhaps there´s a problem with your project.

have you tried to load something else?

regards,

Hi mopS04,

I have tried loading an empty project containing only plc configuration and empty OB1. It works.

Today I have taken the plc to my vendor office: it started to work perfectly. It didn't go into defective state, I could connect, read diagnostic buffer and reload the program. For some reason the same program is not working when plc is on the machine. From what I can see only two things are different: power supply (they connect it to their own) and no module was attached (I brought only the plc not the entire rack). In the plc rack there are the following modules: master profibus module, power module, 5 DI and 5 DO modules.