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or the components connected in the network will function correctly.
Note
Data of the “WORD“ (2 bytes) or "DWORD“ (4 bytes) type are stored in an S7-200
in "big-endian“ format, i.e.
Address n: MSB
Address n+1: LSB (analogous for DWORD).
4.4.1 Occupied system flag area (SM area)
The CP 243-1 occupies 50 bytes in the S7-200 CPU system flag area. The address
of these 50 bytes depends on the position in which a CP 243-1 is currently located
in an S7-200 system. Primarily general information and status information of the
CP 243-1 are stored in these 50 bytes. The last four bytes contain a pointer
through which one can access the CP 243-1 configuration data. These configuration
data is consecutively stored in the S7-200 CPU variables memory. They are
subpided into the:
• Configuration Data Block (CDB)
• Network Parameter Block (NPB)
• Network Data Block (NDB)
The following table shows the relationship between the position of a module in the S7-200 system and the associated system flag area.
Table 2: System flag area
Note
When using firmware version less than 1.20 then the CP 243-1 must be in position
0 (next to the CPU) or it may be in position 1 if another intelligent module occupies
position 0.
4.4.2 Structure of the Configuration Data Blocks (CDB)
The CDB is generated by the Ethernet Wizard in STEP 7 Micro/WIN 32. The following
table shows the structure of the CDB.
4.4.3 Structure of the Network Parameter Blocks (NPB)
This data block is generated by the CP 243-1 itself in accordance with the current
set of network parameters. It contains the TCP/IP parameter values currently in
use, provided the CP 243-1 has been correctly configured. In the event of a configuration
error, the NPB will not contain any valid data.
4.4.4 Structure of the Network Data Blocks (NDB)
The NDB is generated by the Ethernet Wizard in STEP 7 Micro/WIN 32. The
read/write commands possible for clients are configured in this data bock. Up to 32
read/write commands can be configured for each of the 8 possible communication
channels. If the CP 243-1 is operated on a channel as a server, then there is no
entry in the NDB structure for this channel.
The following table shows the structure of the NDB. The codes for read/write commands
are represented by the letters n, m, p = 0, ..., 31, and the channel codes are
represented by the letter r = 0, ...,7.
4.5 Configuring a communication partner with STEP 7
Using the S7-300 system as an example, the following section outlines the steps
you need to take in STEP 7 to configure the system for communication with an
S7-200 system via the associated Ethernet communications processor. The procedure
for the S7-400 system is similar.
For the exact configuration steps, please refer to the STEP 7 description (MLFB:
6ES7 810-4CC05-0YX0) or the handbooks for the CP 343-1 and the CP 443-1.
In S7-300 and S7-400 systems, a distinction is made between configured and free
connections. For configured connections, the connection parameters are specified
by the user. In contrast, free connections do not have to be configured in STEP 7.
Configured connections
If you would like to work with a configured connection, you must first insert a new
S7 connection in the STEP 7 NetPro program package. In the "Insert new connection"
mask, specify the type of station with which you would like to establish a connection.