Technical data

Table Of Contents
System Software for S7-300/400 System and Standard Functions - Volume 1/2
A5E00709327-01
7-1
7 SFCs/SFBs for Transferring Data Records
7.1 Writing and Reading Data Records
Principle
Some modules have a write-only system data area to which your program can
transfer data records. This area contains data records with numbers from 0 to a
maximum of 240. Not every module contains all of the data records (see following
table).
Other modules have a read-only system data area in which your program can read
data records. This area contains data records with numbers from 0 to a maximum
of 240. Not every module contains all of the data records (see following table).
Note
There are modules that have both system data areas. These are physically
separate areas and all they have in common is their logical structure.