Siemens Simatic S7-300 CP 341 User Manual page 174

Communication via Function Blocks
6.7 Parameter assignment of the Function Blocks
Parameter assignment of data words
The specification of data words (partially qualified specification) is not allowed because
(depending on the actual operands) the currently selected data block can no longer be
determined in the standard function. If a data operand is specified as an actual parameter,
the fully qualified specification must always be used.
A fully qualified specification can be either absolute or symbolic. Mixed addressing with fully
qualified data operands is rejected by the compiler.
Example 1
The symbol name for the data block is entered in the symbol table, while the symbol name
for the data operand is declared in the corresponding data block.
STL
DB 10.DBW 0
CP_DB.SEND_DWNR
Example 2
The symbol name of the data block used, DB 10, is "CP_DB"; the symbol name for the send
DB number is "SEND_DBNO" and is located in data block DB 10 in data word DBW 0.
The start address of the send message frame is "SEND_DWNO" and is located in data block
DB 0 in DBW 2, and the message frame length is "SEND_LEN" and is located in data block
DB 10 in DBW 4.
The variable used for the module address is the memory word "BGADR" (MW21), for the
DONE parameter the memory bit "SEND_DONE" (M26.0), for the ERROR parameter the
memory bit "SEND_ERROR" (M26.1), and for the STATUS parameter the memory word
"SEND_STATUS" (MW27).
The STL listings for the example are shown on the following page.
174
www.gkbpx.com
Absolute fully qualified addressing
Symbolic fully qualified addressing
CP 341 Point-to-Point Communication, Installation and Parameter Assignment
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Manual, 09/2008, A5E02191071-01