Variable inside S7-400 PLC software

electrician1

Hi

Inside one of the block I have come across variable L30.7 which I’m not able to trace back.Can somebody explain what it is . Attached is screen shoot

There's a difference between local data (TEMP) of an FB and STAT data.

The STAT (STATic) variablesare located in the instance data block which is assigned to the called FB and confusingly can be referred to as local data of FB in help files.

The TEMP (local data) is part of the CPU system memory that you can use for scratching (TEMPorarily)but not for storing data.

When you move MD1500 to STAT it means you move it to a double word register in the instance data block.

richardstarr

However if MD 1500 is equal to zero, I get none zero values for some of the local bits.

When you access L12.0 it means you are trying to access a bit in local memory (TEMP) which might not be clean and needs to be intialized.