Siemens programming the cpu 314c-2dp User Manual
Automation and Drives - SCE
T I A Training Document
Page 10 of 25
Module
Retentivity
Your CPU 31xC has retentive memory. Retentivity is implemented on the MMC and on the CPU.
Due to this retentivity, the contents of the retentive memory are retained even after the mains supply
has been switched off and the CPU has been restarted (warm restart).
Your CPU 31xC has retentive memory. Retentivity is implemented on the MMC and on the CPU.
Due to this retentivity, the contents of the retentive memory are retained even after the mains supply
has been switched off and the CPU has been restarted (warm restart).
Load memory
You program in the load memory (MMC) is always retentive. During loading, it is stored on the MMC,
is powerfail-proof and cannot be cleared.
You program in the load memory (MMC) is always retentive. During loading, it is stored on the MMC,
is powerfail-proof and cannot be cleared.
Work memory (RAM)
Your data in the work memory are backed up on the MMC in the event that the mains supply is
switched off. The contents of data blocks are therefore always retained.
Your data in the work memory are backed up on the MMC in the event that the mains supply is
switched off. The contents of data blocks are therefore always retained.
System memory
With regard to clock memories, timers and counters, you configure (properties of the CPU,
Retentivity tab) which parts are to be retentive and which are to be initialized with "0" when the
system is restarted (warm restart).
The diagnostic buffer, MPI address (and baud rate) as well as the runtime meter are generally stored
in the retentive memory area on the CPU. The retentive area for the MPI address and the baud rate
ensure that your CPU is still able to communicate after a power failure, a complete memory reset or
loss of the communication parameters (because the MMC was removed, or the communication
parameters were deleted).
With regard to clock memories, timers and counters, you configure (properties of the CPU,
Retentivity tab) which parts are to be retentive and which are to be initialized with "0" when the
system is restarted (warm restart).
The diagnostic buffer, MPI address (and baud rate) as well as the runtime meter are generally stored
in the retentive memory area on the CPU. The retentive area for the MPI address and the baud rate
ensure that your CPU is still able to communicate after a power failure, a complete memory reset or
loss of the communication parameters (because the MMC was removed, or the communication
parameters were deleted).
Retention of the memory objects
The following table shows which memory objects are retained when transitions between operating
modes occur.
The following table shows which memory objects are retained when transitions between operating
modes occur.
Memory Object
Operating Mode Transition
PowerOn/PowerOff
STOP
Æ
RUN
Memory
Reset
Reset
User Program/User Data (load memory)
X
X
X
Actual values of the DBs
X
X
-
Flags, timers and counters configured as
retentive
retentive
X X
-
Diagnostic buffer, hours run meter
X
X
X
MPI address, baud rate
X
X
X
X = retentive; - = not retentive
Foreword Notes
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n STEP 7 program
Testing
A5
Issue date: 02/2008 Programming the CPU 314C-2DP