Start-up Characteristics and Operating Mode Transitions of the CP 341
7.3 Behavior of the CP 341 on Operating Mode Transitions of the CPU
CP 341 Point-to-Point Communication, Installation and Parameter Assignment
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Manual, 09/2008, A5E02191071-01
7.3
Behavior of the CP 341 on Operating Mode Transitions of the CPU
Once the CP 341 has been started up, all data is exchanged between the CPU and the
CP 341 by means of the function blocks.
General procedure
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 341 is continued with the ASCII driver and the printer
driver in the case of parameter assignment without flow control. In other words, the current
send request will still be completed. In the case of the ASCII driver, receive message frames
continue to be received until the receive buffer is full.
CPU START-UP
On start-up, the CP sends the parameters created with the CP 341: Point-to-Point
Communication, Parameter Assignment parameter assignment interface. The CP 341
carries out a parameter reassignment only if parameters have changed.
CPU RUN
When the CPU is in RUN mode, send and receive operations are unrestricted. In the first FB
cycles following the CPU restart, the CP 341 and the corresponding FBs are synchronized.
No new FBs or FCs can be executed until this process has been completed.
Special features for sending message frames and for printout
Message frames can only be sent when the CPU is in RUN mode.
If the CPU changes to STOP mode during the CPU > CP data transmission, the FB
P_SND_RK or the FB P_PRINT_RK reports the error "current program interrupted, request
aborted due to BREAK/restart/reset" following the restart.
Note
The CP 341 sends data to the communication partner only after it has received all the data
from the CPU.
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