siemens step 7 memory management

[controlsdude]

does anyone have a rule of thumb on laying out the address memory area in the symbol table for step 7?

If you have Bool's do you usually put them in M 1-100
Word's in M 102-200?

I have a few examples from past programs or projects. But it seems all over the place in the memory map.

I am really getting to hate this memory layout, reminds me of Allen Bradley plc2.

 

[mikek10]

It doesn't particularly matter as long as you make the appropriate documentation / records.

Do whatever fits in with your companies policy/past works (if any) and your customers (if any).

 

[CanadianTaff]

Are you talking about S7-200 or the 300/400 ranges.

If you are talking S7-300/400, then planning memory in M memory area seems limited, most data is held in DB's especially with the use of FB's and STAT's.

In S7-200, I have no idea.

 

[MifPT]

In the S7-200 is you that decide were to put bits and bytes.
Usually I also divide the first area do bits and use the rest of memory to bytes.

So, the answer to your question is YES, personnally I use M0 to M100 bits and M102 to the end of bytes.

Also, usually I use continuos bits/bytes.
If in your program the bytes used are all over the place this is bad programming.

Don't forget of the size of the variable you are using, if is a word you will need two bytes, if is a dword you will need four bytes !!!

Regards,
Miguel