Siemens S7-1500 Function Manual page 16

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. The work memory is only used
in operation of the CPU.
In the 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.
Tags of global data blocks, instance data blocks and technology objects are initialized
with their start values at the operating states changes below. Retentive tags receive their
actual values saved in the retentive memory.
– POWER ON → STARTUP
– STOP → STARTUP
Work memory of CPU 1518-4 PN/DP MFP and CPU 1518F-4 PN/DP MFP
Additional work memory is needed for use of the CPU function libraries and C/C++ runtime
applications.
Retentive memory
The retentive memory is non-volatile memory for saving a limited amount of data in the event
of power failure.
The following actions delete certain memory objects of the retentive memory:
● Memory reset
● Reset to factory settings
You can find an overview of the retentive behavior of the individual memory objects in
section Retentive behavior of the memory objects (Page 30).
You can find additional information on the memory reset and reset to factory settings
functions in the following manuals:
● System manual S7-1500, ET 200MP Automation System
(http://support.automation.siemens.com/WW/view/en/59191792)
● System manual ET 200SP Distributed I/O System
(http://support.automation.siemens.com/WW/view/en/58649293)
● Operating instructions ET 200pro CPU 1516pro-2 PN
(https://support.industry.siemens.com/cs/ww/en/view/109482416)
Structure and Use of the CPU Memory
Function Manual, 10/2018, A5E03461664-AC
Memory areas and retentive memory
2.1 Memory areas
15