QUESTION:
Why does offline information vary in part substantially from information in the online mode of the module?

ANSWER:
In STEP 7 let object properties of the block folder show you the required memory of code and data memory.

Fig. 1: Properties of Block Folder Offline

When loading the program into CPU, the values of the online mode of the module vary in part substantially from those calculated in the offline view of STEP 7.
The offline view only shows static information of the (user) module, not system data information of the block (SDB). In this view, the dynamically used system ressources of the user data blocks as well as the dynamic system ressources of the alarm blocks are unavailable as well.

Fig. 2: Module Information - ONLINE

Explanation:
The size of the load memory is the sum of the block size (offline view) plus the sum of SDBs (these are shown in the SDB folder).
The work memory code is different before and after the first start-up.
Prior to the first start-up the code requirement of work memory is the sum of:
code requirement of blocks
+ code requirement of communication blocks
+ code requirement of PAE
+ code requirement of PAA
+ code requirement of diagnostics buffer
After the first start-up, the requirement of communication data is added.
The work memory requirement of data is independent of the first start-up. This is determined by the dynamics of the user program and is the sum of:
data requirement of blocks (offline view)
+requirement of system data
+user blocks created by SFC
+local data requirement (configuration)

The catalogue specifications of available code and data memory always refer to default settings of the CPU within the Hardware Configuration. E. g. , if process imaging is expanded within CPU Properties, this will draw on free work memory of code. Same applies to the maximum number of communication batches and to the number of messages in the diagnostics buffer.

Fig. 3: Details on Work Memory of Code

The following table states the additional memory requirement in the work memory of code for expanding the ressources:

Ressource	Additional need in work memory code
per additional byte of PAE/ PAA	12 byte
per additional communications ressource	72 Byte
per additional message in the diagnostics buffer	20 byte

Table 1: Additional Memory Requirement in the Code Memory

Similar applies to the memory requirements of data in the work memory. In addition system data, local data and data blocks created by SFC are stored here.

Keywords:
PAE, PAA