Specifications

CPU Memory: Data Types and Addressing Modes
5-15
S7-200 Programmable Controller System Manual
C79000-G7076-C233-01
5.3 Memory Retention for the S7-200 CPU
The S7-200 CPU provides several methods to ensure that your program, the
program data, and the configuration data for your CPU are properly retained. See
Figure 5-11.
 The CPU provides an EEPROM to store permanently all of your program,
user-selected data areas, and the configuration data for your CPU.
 The CPU provides a super capacitor that maintains the integrity of the RAM
after power has been removed from the CPU. Depending on the CPU, the
super capacitor can maintain the RAM for several days.
 The CPU supports an optional battery cartridge that extends the amount of time
that the RAM can be maintained after power has been removed from the CPU.
The battery cartridge provides power only after the super capacitor has been
drained.
This section discusses the permanent storage and retention of the data in RAM
under a variety of circumstances.
RAM: maintained by the super capacitor
and the optional battery cartridge
EEPROM: provides
permanent storage
User program
V memory
(permanent area)
CPU configuration
M memory
(permanent area)
User program
V memory
CPU configuration
M memory
Timer and Counter
current values
Figure 5-11 Storage Areas of an S7-200 CPU
Downloading and Uploading Your Project
Your project consists of three elements: the user program, the data block
(optional), and the CPU configuration (optional). As shown in Figure 5-12,
downloading the project stores these elements in the RAM area of the CPU
memory. The CPU also automatically copies the user program, data block (DB1),
and the CPU configuration to the EEPROM for permanent storage.