Siemens SIMATIC S7-400 Reference Manual page 33

Changing the Memory Card
To change the memory card, follow the steps outlined below:
1. Set the CPU to STOP.
2. Remove the plugged in memory card.
Note
If you remove the memory card, the CPU requests a memory reset by flashing the
STOP indicator every three seconds. This sequence cannot be influenced by error
OBs.
3. Insert a "new" memory card.
4. Perform a memory reset on the CPU.
Automation System S7-400 CPU Specifications
A5E00165965-01
Structure of a CPU 41x
1-21