Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual page 134

Commissioning
8.4 Commissioning the Modules
How to reset memory
There are two ways to reset CPU memory:
CPU memory reset using the mode selector
switch
... is described in this chapter.
Resetting CPU memory with mode selector switch
The table below shows the steps in resetting CPU memory.
Table 8-4
Step
1.
2.
3.
The procedure described in the table above is only required if the user wishes to reset the
CPU memory without being requested by the CPU to reset the memory (STOP LED flashing
slowly). If the CPU prompts you for a memory reset, you only have to turn the mode selector
briefly to MRES position to initiate the memory reset operation.
The figure below shows how to use the mode selector switch to reset CPU memory:
STOP-
LED
on
off
If the CPU prompts you for another memory reset following a successful memory reset
operation, the MMC may need to be reformatted in certain cases (
Memory Card (MMC)
8-10
Procedure for CPU memory reset
Reset CPU memory
Turn the key to STOP position
Turn the key to MRES position Hold the key in this position until the STOP LED lights up
for the second time and remains on (this takes 3 seconds). Now release the key.
You must turn the key to MRES position again within 3 seconds and hold it there until the
STOP LED flashes (at 2 Hz). You can now release the switch. When the CPU has
completed memory reset, the STOP LED stops flashing and remains lit.
The CPU has reset the memory.
3 s
1 2
).
CPU memory reset using the PG
... is only possible when the CPU is in STOP
STEP 7 Online Help
(see
max. 3 s
3
Operating Instructions, Edition 08/2004, A5E00105492-05
).
min. 3 s
CPU
see Formatting a Micro
S7-300, CPU 31xC and CPU 31x: Installation
t