The specifications for the communications end points ("TSAPs") in STEP 7 and in

Enabling / disabling the CRC mechanism and defining the Keep Alive time

Once you have configured the connections, you must specify in the next dialog

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 continues

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 communication partners.

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 recognize

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 dialog you also can set a common monitoring time (Keep Alive time)

for all configured connections. The value entered here determines the time after

which the CP 243-1 IT recognizes the communication problem described in chapter

2.3.3

You have already specified which connections are to be monitored with this time

when you configured the inpidual connections.

Defining the memory area for storing the configuration

Finally, use the next dialog to define the memory area in which your configuration

data is to be stored on the S7-200 CPU. The Wizard will assist you in doing so.

The Wizard then informs you about which subroutines it is establishing on the basis

of your configuration and where your configuration data is being stored.

Configuration of the system is now complete.

Attention

Ensure that the memory area in which the Ethernet Wizard stores the configuration

data is not used by your S7-200 user program.

4.4 Configuring a CP 243-1 from a user program

The configuration data of the CP 243-1 is stored in the S7-200 CPU memory and

can therefore be changed directly from an S7-200 user program. The cyclic redundancy

check (CRC) must be disabled for the configuration data so that the

CP 243-1 will accept configuration data which was changed in this way during the

next startup. For this purpose, the value 16#AC must be entered for Byte 13 of the

CDB data structure. This takes place automatically as soon as the CRC mechanism

is switched off in the Ethernet Wizard.

Attention

Configuring the CP 243-1 from a user program is only recommended for experienced

programmers.

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