Siemens SIMATIC S7-400 CP 440 - Behavior of the CP 440 on Operating Mode Transitions of the CPU

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Startup Characteristics and Operating Mode Transitions of the CP 440

7.3 Behavior of the CP 440 on Operating Mode Transitions of the CPU

Point-to-point connection CP 440 Installation and Parameter Assignment

Manual, 09/2007, A5E00057742-03

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7.3 Behavior of the CP 440 on Operating Mode Transitions of the CPU

Once the CP 440 has been started up, all the data is exchanged between the CPU and the

CP 440 via the function blocks.

CPU STOP

In CPU STOP mode, communication via the S7 backplane bus is not possible. Any active

CP CPU data transmission, including both send and receive message frames, is aborted and

the connection is reestablished.

Data traffic at the interface of the CP 440 is continued with the ASCII driver in the case of

parameter assignment without flow control. In other words, the current send request is

completed. Receiving the data depends on the setting of the basic parameter "Reaction to

CPU Stop".

CPU STARTUP

On start-up, the CP sends the parameters created with the CP 440: Point-to-Point

Communication, Parameter Assignment programming interface. The CP 440 only parameter

reassignment if the parameters have changed.

CPU RUN

When the CPU is in RUN mode, sending and receiving are unrestricted. In the first FB cycles

following the CPU restart, the CP 440 and the corresponding FBs are synchronized. No new

FB is executed until this is finished.

Points to Note when Sending Message Frames

Message frames can be sent only when the CPU status is RUN.

If the CPU goes into STOP during data transmission from the CPU " CP, the SEND_440 FB

reports after restart that the current program has been interrupted and the job has been

terminated due to BREAK/restart/reset.

Note

The CP 440 does not send data to the communications partner until it has received all data

from the CPU.

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