Operations In The Cpu During A Memory Reset - Siemens SIMATIC S7-300 Hardware And Installation Manual

What happens in the CPU during memory reset?
Table 9-5

Operations in the CPU during a memory reset

Event CPU 312 / 313 / 314 / 314 IFM (314-5AE10) / 315 / 31x-
CPU activities 1. The CPU deletes the complete user program in main memory and RAM load
memory.
2. The CPU deletes the retentive data.
3. The CPU tests its own hardware.
4. If a Memory Card or an MMC is inserted, the CPU
copies its runtime relevant data to main memory.
Tip: If the CPU cannot copy the data on Memory Card
or MMC and requests memory reset:
•
•
•
Memory contents The status of CPU memory space is "0". If a Memory Card
after reset or MMC has been inserted, the user program is transferred
again to main memory.
What's left? Data in the diagnostics buffer.
You can read the diagnostic buffer with the PG (see STEP 7 Online Help).
The MPI parameters (MPI address and highest MPI address, transmission rate,
configured MPI addresses of CPs/FMs in an S7-300).
The contents of the operating hours counter (not for CPU 312 IFM).
Special feature: MPI parameters
MPI parameters hold a special position when memory is reset. The table below
describes MPI parameters remaining valid after memory reset.
Memory reset ...
with micro memory card (MMC) inserted
With integrated FEPROM load memory
(CPU 312 IFM / 314 IFM (314-5AE0x)
without micro memory card (MMC) inserted
S7-300 Programmable Controller Hardware and Installation
A5E00105492-02
2 DP / CPU 31xC
Remove the Memory Card or MMC
Resetting CPU memory
Read the diagnostic buffer.
CPU 312 IFM /
314 IFM (314-5AE0x)
The CPU copies
runtime relevant data
from EPROM memory
to main memory
The user program is
loaded back into the
RAM from the
integrated retentive
EPROM of the CPU.
MPI parameters
... located on the memory card or on the
integrated FEPROM of the CPU are valid. If
this location does not contain parameter
data (SDB), the previously set parameters
stay valid.
... are retained and valid.
Commissioning
9-19