S7 Receives Data From A Communication Partner - Siemens Simatic S7-300 CP 341 User Manual

Communication via Function Blocks
6.3 Using the Function Blocks with the 3964(R) Procedure
6.3.2

S7 receives data from a communication partner

The FB P_RCV_RK transmits data from the CP 341 to an S7 data area, specified by the
DB_NO, DBB_NO, and LEN parameters. For purposes of data transmission, the
FB P_RCV_RK is called cyclically or, alternatively, statically in a time-driven program
(without conditions).
A (static) signal state "1" at the EN_R, parameter enables a check to determine whether data
can be read from the CP 341. An active transmission can be canceled with signal state "0" at
the EN_R parameter. The canceled receive request is terminated with an error message
(STATUS output). Receiving is disabled as long as the signal state at the EN_R parameter is
"0". A data transmission operation can run over several calls (program cycles), depending on
the amount of data involved.
If the function block recognizes signal state "1" at the R parameter, the current transmission
request is canceled and the FB P_RCV_RK is placed in its initial state. Receiving is disabled
as long as the signal state at the R parameter is "1".
The LADDR parameter defines the CP 341 to be addressed.
Error display at the FB P_RCV_RK
The NDR output shows "request completed without errors/data accepted" (all data read).
ERROR indicates whether an error has occurred. If an event has occurred, the
corresponding event number is displayed in STATUS. If no error has occurred, STATUS has
the value 0. NDR and ERROR/STATUS are also output in response to a RESET of the FB
P_RCV_RK (LEN parameter == 16#00). The binary result BR is reset after an error has
occurred. If the block has been completed without errors, the binary result has the status "1".
Note
The P_RCV_RK function block does not have a parameter check. If the parameter
assignment is incorrect, the CPU can go to STOP mode. Before the CP 341 can receive a
request after the CPU has changed from STOP to RUN mode, the CP-CPU start-up
mechanism of the FB P_RCV_RK must have been completed.
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CP 341 Point-to-Point Communication, Installation and Parameter Assignment
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Manual, 09/2008, A5E02191071-01