Siemens SIMATIC NET CP 243-1, Operating Instructions Manual

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Configuration
3.4 Other options when configuring a CP 243-1
CP 243-1
Operating Instructions, 03/2012, C79000-G8976-C244-02
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3.3.5 Completing configuration
During completion of the configuration of the CP 243-1, the Internet wizard sets up all
required subroutines so that an S7-200 user program can access the CP 243-1 as specified
in the configuration. This means that the subroutine required to enable a certain service is
only set up if this service was actually configured.
3.4 Other options when configuring a CP 243-1
Some of the configuration data of the CP 243-1 is stored in the memory of the S7-200 CPU
while some is stored in the file system of the CP 243-1.
The memory of the S7-200 CPU contains the Ethernet configuration and the basic settings
(for example enabling or disabling individual IT services) made for an IT configuration. While
it is starting up, the CP 243-1 reads this part of the configuration from the memory of the S7-
200 CPU and evaluates it (during ongoing operation, it monitors it continuously for changes)
The IT-specific configurations consisting of the configuration of the e-mail client, the FTP
client and the user administration are stored in the file system of the CP 243-1 in the
directory /flash:/config in files with the extensions .edb, .fdb and .udb.
Each one of these configuration files has a TIMESTAMP element containing a time stamp
that is read cyclically by the CP 243-1. If the CP 243-1 detects that a TIMESTAMP element
has changed since it was read the last time, the file involved is read completely and the CP
243-1 reconfigures itself dynamically with the configuration in this file. This means that a
change in one of the three configuration files only affects the CP 243-1 if the TIMESTAMP
element was also changed.
Access to the configuration data in the memory of the CPU
The configuration data stored in the memory of the S7-200 CPU can also be changed
directly by an S7-200 user program. For the CP 243-1 to accept configuration data changed
in this way when it restarts, the CRC protective mechanism for configuration data must be
disabled. The value 16#AC must be entered in byte 13 of the CDB data structure. This
happens automatically as soon as the CRC mechanism is disabled in the Internet wizard.
NOTICE
Configuration of the CP 243-1 by a user program is only recommended for experienced
programmers.
Since, after the CRC check is disabled, the CP 243-1 is no longer able to check the
configuration data on the S7-200 CPU completely for consistency in terms of desired and
undesired changes, there is no guarantee whatsoever in this use case that the CP or the
components connected to the network will function correctly.