CPU Memory: Data Types and Addressing Modes
5-17
S7-200 Programmable Controller System Manual
A5E00066097-02
Automatically Saving the Data from the Bit Memory (M) Area When the CPU
Loses Power
If the first 14 bytes of M memory (MB0 to MB13) are configured to be retentive,
they are permanently saved to the EEPROM when the CPU loses power. As
shown in Figure 5-14, the CPU moves these retentive areas of M memory to the
EEPROM. In STEP 7-Micro/WIN 32, the default setting is set to off.
RAM EEPROM (Permanent)
User program
V memory
(permanent area)
CPU configuration
M memory
(permanent area)
First 14 bytes of M memory
(MB0 to MB13), if configured to be
retentive, are copied to the
EEPROM when the CPU loses
power.
User program
V memory
CPU configuration
M memory
Timer and counter
current values
Figure 5-14 Saving Parts of Bit Memory (M) to EEPROM on Power Off
Retaining Memory on Power On
At power on, the CPU restores the user program and the CPU configuration from
the EEPROM memory. See Figure 5-15.
EEPROM (Permanent)
User program
V memory
CPU configuration
M memory
Timer and Counter
current values
User program
CPU configuration
User program
V memory
(permanent area)
CPU configuration
M memory
(permanent area)
RAM
Figure 5-15 Restoring the User Program and CPU Configuration on Power On
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