Retentive Behavior Of The Memory Objects - Siemens SIMATIC S7-300 Manual

The diagnostics buffer, MPI address (and transmission rate) and operating hour counter data
are generally written to the retentive memory area on the CPU. The retentive address areas
of the MPI address and transmission rate ensures that your CPU can continue to
communicate, even after a power loss, memory reset or loss of communication parameters
(e.g. due to removal of the MMC or deletion of communication parameters).
Working memory
The retentive data in the working memory are saved to a non-volatile memory on the CPU
during POWER OFF. Therefore, contents of retentive DBs are always retentive.
With the Technology CPU, non-retentive DBs are also supported (the non-retentive DBs are
initialized at restart and POWER OFF-ON with their initial values from the load memory).
Technology system data
The technology system data are always stored as retentive data in the load memory of the
CPU.
6.1.3

Retentive behavior of the memory objects

Retentive behavior of the memory objects
The table below shows the retentive behavior of memory objects during specific operating
state transitions.
Table 6-1
Memory object
User program/data (load memory)
•
•
Flags, timers and counters configured as
retentive data
Diagnostics buffer, operating hour counters
MPI/DP address, transmission rate
(or also DP address, transmission rate of
the Technology CPU MPI/DPinterface, if
this is parameterized as DP node).
Technological parameters
•
•
x = retentive; - = non-retentive
S7-300 CPU Data: CPU 315T-2 DP
Manual, 12/2005, A5E00427933-02
Retentive behavior of the memory objects
Retentive behavior of the DBs (without
technology DB)
Retentive behavior of the technology
DBs
Changed with FB "MC_WriteParameter"
S7TConfig
Changed with
6.1 Memory areas and retentive address areas
Operating state transition
POWER ON /
POWER OFF
X
Can be set in the Properties of the
DBs.
-
X
X
X
-
X
Memory concept
STOP → CPU memory
RUN reset
X X
-
- -
X -
X X
X X
X -
X X
6-3