Table 10- 1 Memory Requirements - Siemens SIMATIC S7-400H System Manual

Basis for Calculating the Required Working Memory
To ensure that you do not exceed the available amount of working memory on the CPU, you
must take into consideration the following memory requirements when assigning parameters:
Table 10- 1 Memory requirements
Parameter
Size of the process image
(inputs)
Size of the process image
(outputs)
Communication resources
(communication jobs)
Size of the diagnostics buffer
Quantity of local data
Flexible memory space
● Work memory:
● Load memory:
Backup
● The backup battery provides backup power for the integrated and external part of the
S7-400H
System Manual, 03/2012, A5E00267695-11
Required working memory
20 bytes per byte in the process image of inputs
20 bytes per byte in the process image of inputs
72 bytes per communication job
32 bytes per entry in the diagnostics buffer
1 byte per byte of local data
The capacity of the work memory is determined by selecting the appropriate CPU from
the graded range of CPUs.
The integrated load memory is sufficient for small and medium-sized programs.
The load memory can be increased for larger programs by inserting the RAM memory
card.
Flash memory cards are also available to ensure that programs are retained in the event
of a power failure even without a backup battery. Flash memory cards (8 MB or more) are
also suitable for sending and carrying out operating system updates.
load memory, the data section of the working memory and the code section.
10.1 Overview of the memory concept of S7-400H CPUs
Memory concept
In code/data memory
Code memory
Code memory
Code memory
Code memory
Data memory
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