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Siemens Step 7 declaring local variables

Siemens Step 7 declaring local variables

(OP)
I am somewhat new to Step 7, but not to PLC's. I seem to have a problem grasping the concept here when it comes to the inputs and outputs of what Siemens calls the "Variable Declaration Table". Are these I/O real physical inputs and outputs?

RE: Siemens Step 7 declaring local variables

These are the local variables assigned to the FC,FB, or OB blocks. Your physical I/O are symbolically assigned in the 'Symbol table'.

RE: Siemens Step 7 declaring local variables

Rockwell Contrologix AB
If your familar with AB then it would be something similar to an AOI, where the variables are local to that routine. Or program tags as it relates all the routines that are associated with that particular task. Then your aliasing the program tags to controlller scope tags.

If your really old as dirt then think about AB PLC2 series, its the same concept.

Just remember you have to map in/out to global variables in step 7 for it to see it used anywhere else besides that routine.

But I thought Seimens updated this concept because when I used it, it was not very friendly or intuitive, but geared toward how a certain country in europe thought.

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