Siemens Simatic S7-400

S7-400 Automation System, CPU Specifications
Manual, 10/2006, 6ES7498-8AA04-8BA0
8-1
Storage Concept and Startup Types
8
8.1 Overview of the memory concept of S7-400 CPUs
Organization of Memory Areas
The memory of the S7 CPUs can be divided into the following areas:
Load memory
For project data (blocks, symbols,
comments, configuration and parameter
assignment data)
Working memory
For runtime-relevant blocks
or
retentive flash memory
Integrated load memory
RAM with battery backup
Diagnostic buffer
Local data stack
RAM with battery backup
Working memory code
For the program
RAM with battery backup
Process Image of Inputs
And Outputs
Working memory data
for data
RAM with battery backup
System memory
Contains flags, timers, counters,
Block stack and
interrupt stack
External load memory
RAM with battery backup
Figure 8-1 Memory areas of the S7-CPUs