Technical data

Memory areas and retentive memory
2.3 Summary of retentive behavior
Structure and Use of the CPU Memory
16 Function Manual, 01/2013, A5E03461664-01
2.3 Summary of retentive behavior
Retentive behavior of the memory objects
This chapter gives an overview of the retentive behavior of memory objects for S7-1500
CPUs. Besides the retentive memory areas described so far, there are additional objects
with retentive behavior, such as the diagnostic buffer. These objects do not allocate any
storage space in the retentive memory.
The following table shows the retentive behavior of the memory objects at the operating
mode transitions STOP to startup and POWER ON to startup, as well as the memory-
influencing functions Memory Reset and Reset to Factory Settings.
Table 2- 1 Retentive behavior of the memory objects
Operating mode transitions
Memory object
STOP → STARTUP POWER ON →
STARTUP
Memory reset Reset to factory
settings
Actual values of the data blocks,
instance data blocks
Can be set in the Properties of the DB in
STEP 7.
1
- -
Bit memories, timers and counters
-configured as retentive data
x x - -
Bit memories, timers and counters
- configured as non-retentive
- - - -
Certain retentive tags from
technology objects
(for example, adjustment values of
absolute encoders)
x x x -
Diagnostic buffer entries
(retentive area)
x x x -
Diagnostic buffer entries
(non-retentive area)
x - - -
Operating hours counter x x x -
Clock time x x x -
x = content is retained
– = object is initialized
1) For DBs with optimized access the retentive behavior is configurable for specific tags.