Memory Areas, Addressing And Data Types - Siemens SIMATIC S7-1200 Manual

4.4

Memory areas, addressing and data types

The CPU provides the following memory areas to store the user program, data, and
configuration:
● Load memory is non-volatile storage for the user program, data and configuration. When
● Work memory is volatile storage for some elements of the user project while executing
● Retentive memory is non-volatile storage for a limited quantity of work memory values.
Use the optional SIMATIC memory card either as a program card or as a transfer card.
● Use the transfer card to copy your project to multiple CPUs without using STEP 7. The
● The program card takes the place of CPU memory; all of your CPU functions are
● You can also use the program card for collecting data log files (Page 110). The program
Note
The program card must remain in the CPU. If you remove the program card, the CPU goes
to STOP mode.
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Manual, 11/2011, A5E02486774-04
a project is downloaded to the CPU, it is first stored in the Load memory area. This area
is located either in a memory card (if present) or in the CPU. This non-volatile memory
area is maintained through a power loss. You can increase the amount of load memory
available for data logs by installing a memory card.
the user program. The CPU copies some elements of the project from load memory into
work memory. This volatile area is lost when power is removed, and is restored by the
CPU when power is restored.
The retentive memory area is used to store the values of selected user memory locations
during power loss. When a power down or power loss occurs, the CPU restores these
retentive values upon power up.
An optional SIMATIC memory card provides an alternative memory for
storing your user program or a means for transferring your program. If you
use the memory card, the CPU runs the program from the memory card
and not from the memory in the CPU.
Check that the memory card is not write-protected. Slide the protection
switch away from the "Lock" position.
transfer card copies a stored project from the card to the memory of the CPU. You must
remove the transfer card after copying the program to the CPU.
controlled by the program card. Inserting the program card erases all of the internal load
memory of the CPU (including the user program and any forced I/O). The CPU then
executes the user program from the program card.
card provides more memory than the internal memory of the CPU. The Web server
function (Page 181) of the CPU allows you to download the data log files to a computer.
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4.4 Memory areas, addressing and data types
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