Siemens Simatic S7-300 CP 341 User Manual page 152

Communication via Function Blocks
6.4 Using the Function Blocks with the RK 512 Computer Connection
Use of interprocessor communication flags
Following receipt of the message frame, the interprocessor communication flags specified in
the RK 512 message frame header are checked. The data is not provided unless the value
of the interprocessor communication flag is "0". When transmission is complete, the function
block sets the interprocessor communication flag to "1" and the interprocessor
communication flag (NDR) is output for one cycle at the function block.
The user program can evaluate the interprocessor communication flag in order to find out if
the provided data can be accessed again. As soon as the data have been processed, the
user must reset the interprocessor communication flag to "0". The communication partner
can now issue a FETCH request again.
What is to be done?
Block call
STL representation
CALL
Note
The parameters EN and ENO are only present in the graphical representation (LAD or FBD).
To process these parameters, the compiler uses the binary result BR. The binary result is set
to signal state "1" if the block was terminated without errors. If there was an error, the BR is
set to "0".
152
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P_RCV_RK, I_RCV_RK
EN_R: =
R: =
LADDR: =
DB_NO: =
DBB_NO: =
L_NO: =
L_OFFSET: =
L_CF_BYT =
L_CF_BIT =
NDR: =
ERROR: =
LEN: =
STATUS: =
CP 341 Point-to-Point Communication, Installation and Parameter Assignment
LAD representation
Manual, 09/2008, A5E02191071-01
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