Occupied Special Memory (Sm Area) - Siemens CP 243-1 Operating Instructions Manual

Configuration
3.4 Other options when configuring a CP 243-1
Note
Data of the type "WORD" (2 bytes) or "DWORD" (4 bytes) is stored on an S7-200 in "big-
endian" format, in other words,
Address n: MSB
Address n+1: LSB (and analogously for DWORD).
Alternative configuration of the IT functions
STEP 7 Micro/WIN 32 is used to create the configuration files for the IT functions. In
principle, these files could also be created or manipulated by a conventional text editor
without STEP 7 Micro/WIN 32. The structures of the configuration files are explained in
chapters Structure of the configuration file for user administration (.udb file) (Page 76),
Structure of the configuration file for the e-mail client (.edb file) (Page 79) and Structure of
the configuration file for the FTP client (.fdb file) (Page 84).
NOTICE
You should use only STEP 7 Micro/WIN 32 to create and change the IT configuration files.
If other tools (for example text editors) are used to create or change these files,
configuration errors may not be detected. In this case, there is no guarantee whatsoever
that the CP 243-1 or the components connected to the network will function correctly.
3.4.1

Occupied special memory (SM area)

The CP 243-1 occupies 50 bytes in the special memory area of the S7-200 CPU. The
address of these 50 bytes depends on the current position at which a CP 243-1 is located in
an S7-200 system. These 50 bytes primarily contain general information and status
information of the CP 243-1. The last four bytes contain a pointer with which the
configuration data of the CP 243-1 can be accessed. This configuration data is located
contiguously in the variable memory of the S7-200 CPU. This can be divided into:
● Configuration data block (CDB)
● Network parameter block (NPB)
● Network data block (NDB)
● Internet data block (IDB)
The following table shows the relationship between the position of a module in the S7-200
system and the related special memory area.
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Operating Instructions, 03/2012, C79000-G8976-C244-02
CP 243-1