Siemens Simatic S7-200 System Manual page 143

Automatically Saving the Data from the Bit Memory (M) Area When the CPU Loses Power
The first 14 bytes of M memory (MB0 to MB13), if configured to be retentive, are permanently
saved to the EEPROM when the CPU module loses power. As shown in Figure 7-14, the
CPU moves these retentive areas of M memory to the EEPROM.
User program
CPU configuration
V memory
M memory
Timer and Counter
current values
Figure 7-14
Retaining Memory on Power On
At power-up, the CPU restores the user program and the CPU configuration from the
EEPROM memory. See Figure 7-15.
User program
CPU configuration
Timer and Counter
current values
Figure 7-15
S7-200 Programmable Controller System Manual
C79000-G7076-C230-02
CPU Memory: Data Types and Addressing Modes
RAM
First 14 bytes of M memory
(MB0 to MB13), if configured to
be retentive, are copied to the
EEPROM when the CPU loses
power.
Saving Parts of Bit Memory (M) to EEPROM on Power Off
RAM
User program
CPU configuration
V memory
M memory
Restoring the User Program and CPU Configuration on Power On
EEPROM (Permanent)
User program
CPU configuration
V memory
(permanent area)
M memory
(permanent area)
EEPROM (Permanent)
User program
CPU configuration
V memory
(permanent area)
M memory
(permanent area)
7-13