105BCommunication processor
12.5 Modbus communication
S7-1200 Programmable controller
606
System Manual, 11/2011, A5E02486680-05
DATA_PTR parameter
The DATA_PTR parameter points to the DB or M address that is written to or read from. If
you use a data block, then you must create a global data block that provides data storage for
reads and writes to Modbus slaves.
Note
The DATA_PTR data block type must allow direct addressing
The data block must allow both direct (absolute) and symbolic addressing. When you create
the data block the "Standard" access attribute must be selected.
Data block structures for the DATA_PTR parameter
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These data types are valid for word reads of Modbus addresses 30001 to 39999, 40001
to 49999, and 400001 to 465536 and also for word writes to Modbus addresses 40001 to
49999 and 400001 to 465536.
–
Standard array of WORD, UINT, or INT data types
–
Named WORD, UINT, or INT structure where each element has a unique name and
16 bit data type.
–
Named complex structure where each element has a unique name and a 16 or 32 bit
data type.
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For bit reads and writes of Modbus addresses 00001 to 09999 and bit reads of 10001 to
19999.
–
Standard array of Boolean data types.
–
Named Boolean structure of uniquely named Boolean variables..
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Although not required, it is recommended that each MB_MASTER instruction have its
own separate memory area. The reason for this recommendation is that there is a greater
possibility of data corruption if multiple MB_MASTER instructions are reading and writing
to the same memory area.
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There is no requirement that the DATA_PTR data areas be in the same global data block.
You can create one data block with multiple areas for Modbus reads, one data block for
Modbus writes, or one data block for each slave station.