Please help me out.

Hello,
I dont know but my PLC is always is STOP mode even when i switch it to RUN mode. Something is wrong and i dont know what. . .
Thank for helping.

Nor does anybody else until you post some information .

PLC type etc ?

A few generic reasons why a PLC of any brand will not go into RUN.

1. Corrupted or non-existent program. Could be from electrical noise or loss of backup battery.

2. Hardware failure. Could be the CPU, the power supply or an I/O module.

3. Fatal error in the program. You have to clear the error before being able to restart. In some PLCs, division by zero can be fatal.

Do you have the software to see if the PLC is in STOP in the program?

I use STEP7 and i dont use any other software to see if the PLC is in STOP.

OK then , open up the processor online and look in the diagnostic buffer - post what you find .It would never have crossed my mind to have mentioned what processor/platform it was in the first place ?!?!

Thanks for the tip, i used module information and i found out that was something wrong with the memmory "STOP caused by CPU memmory management", i checked Help on event. According to the help i had to restart the CPU memmory ... so i used CPU->Diagnostics/Setting->Clear/Reset. Now is working. Again thanks man.

Just a note on this,
Siemens S7 uses some special OB blocks to handle most errors. These are in the range from OB80 and onwards. If an error occurs, the correct block will be called and the program in it run. If the block is missing, the CPU will enter STOP mode. If the block is empty, the PLC will effectively ignore the error and continue running. I reccomend that you program some error trapping code into these blocks that will alert you to your errors without stopping the PLC.