Configuration 09/02
CP 243-1
34 J31069-D0428-U001-A1-7618
Enabling / disabling the CRC mechanism and defining the Keep Alive time
Once you have configured the connections, you must specify in the next mask
whether or not your configuration data on the S7-200 CPU are to be protected by a
CRC mechanism against being unintentionally overwritten.
If the CRC mechanism is enabled, the CP 243-1 checks, while it is booting,
whether its configuration data, which it reads out of the memory of the S7-200
CPU, were overwritten by the user program. If so, it stops booting and attempts to
retrieve its TCP/IP address parameters from a BOOTP server. If successful, it con-
tinues booting. In this case, however, only the MicroWN channel is enabled. Thus,
the CP 243-1 can then only communicate with STEP 7 Micro/WIN 32 but not with
other controllers.
Activating the CRC mechanism is recommended. This is the only way that the
CP 243-1 can recognize unintended changes to the configuration data by the user
program.
If the CRC mechanism is not enabled, you can change the configuration data of
the CP 243-1 in the user program. However, the CP 243-1 will not be able to rec-
ognize if the data have been unintentionally overwritten.
Attention
An S7-200 user program can only be used to configure data if the CRC mechanism
has been switched off.
The CP 243-1 cannot completely check the configuration data for consistency with
regard to intentional and unintentional changes after the CRC check has been
switched off. Therefore, in this case there is no guarantee whatsoever that the CP
or the components connected in the network will function correctly.
In the same mask, you can set the Keep Alive time for all configured connections
at once. If a connection partner should suddenly be unavailable, e.g. if there is a
fault in the TCP/TP network or an error with the communication partner, then the
value entered here is to used to determine the time after which the CP 243-1 will
recognize the problem.
You already defined which connections are to be monitored by this time period
when you configured the individual connections.
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