Siemens SIMATIC S7 System Manual page 109

Risks with STEP 7-Micro/WIN Version 4.0 or greater (.mwp files) with absolute special
memory (SM) addressing
You can open a program (.mwp file) from an earlier version of STEP 7-Micro/WIN in STEP
7-Micro/WIN SMART. If that program uses symbolic special memory (SM) addressing, then
insert the System Symbol table in your project. The symbols map correctly to the current
SM addresses. If, however, the program uses absolute SM addressing, those absolute SM
addresses might no longer exist.
Programs based on inconsistent definitions of SM addresses can result in unexpected
machine or process operation. Unexpected machine or process operation can cause death
or serious injury to personnel, and/or damage to equipment.
If you open an .mwp file in STEP 7-Micro/WIN SMART, delete the "S7-200 Symbols" table
and insert the "System Symbols" table. The symbols in the former .mwp program map to
the current SM address scheme. Convert any absolute SM addresses to use the
corresponding symbol name.
See also
Symbol table (Page 118)
SM (Special Memory) overview (Page 799)
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
WARNING
Programming concepts
5.3 Creating your user program
109