Technical data

Memory areas and retentive memory
2.1 CPU memory areas
Structure and Use of the CPU Memory
10 Function Manual, 01/2013, A5E03461664-01
Load memory
The load memory is a non-volatile memory for code blocks, data blocks, technology objects,
and hardware configuration. When these objects are downloaded to the CPU they are first
saved into load memory. This memory is located on the SIMATIC memory card.
Note
To run the CPU, a SIMATIC memory card must be inserted.
Work memory
The work memory is volatile memory that contains the code and data blocks. The work
memory is integrated into the CPU and cannot be extended.
In the S7-1500 CPUs, the work memory is divided into two areas:
● Code work memory: The code work memory contains runtime-relevant parts of the
program code.
● Data work memory: The data work memory contains the runtime-relevant parts of the
data blocks and technology objects. At the operating mode transitions POWER ON to
startup and STOP to startup, tags from global data blocks, instance data blocks and
technology objects are initialized with their start values; retentive tags retain their actual
values as saved in the retentive memory.
Retentive memory
Retentive memory is non-volatile memory for saving a limited quantity of data in the event of
power failure. The tags and operand areas that have been defined as retentive are saved in
retentive memory. These data is retained beyond a power-off or power failure. All other
program tags are lost under these conditions and are set to their start values upon the
operating mode transitions POWER ON to startup, and STOP to startup.
The content of retentive memory is deleted by the following actions:
● Memory reset
● Reset to factory settings
Specified tags from technology objects are also stored in retentive memory. These tags are
not deleted during memory reset.
You can find additional information on the "Memory reset" topic in the Commissioning
chapter of the S7-1500 Automation System
(http://support.automation.siemens.
com
/WW/view/en/59191792) system manual .