Function code and data type definition
Shows the ABT Site input dialog box of an analog input data point with the corresponding analog input selection of function code and data type.
Function code definition
1 = Read coils
2 = Read discrete inputs
3 = Read holding inputs
4 = Read input register
5 = Write single coil
6 = Write single register
15 = Write multiple coils
16 = Write multiple register
Data type definition available by the function code
To get more information about the encoding of the respective data point, select the link for the desired data point type.
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Function1)/Data type | 3/4 | 3/4 | 6 | 16 | 1/2 | 3/4 | 5/15 | 6/16 | 1/2 | 3/4 | 6/16 | 15 |
B1-B16 |
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B1 |
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B8 |
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B16 |
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U8 |
| x | x |
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U16-B |
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| x | x |
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S16-B |
| x | x |
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F16-B |
| x | x |
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U32-B | x | x |
| x |
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S32-B | x | x |
| x |
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F32-B | x | x |
| x |
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U48-B | x | x |
| x |
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S48-B | x | x |
| x |
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U64-B | x | x |
| x |
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S64-B | x | x |
| x |
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F64-B | x | x |
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1) The numbers in the cell, for example, 3/4 means that the Read holding inputs and Read input register function codes are supported.
Summary of supported MODBUS function codes
Supported and recommended mapping
Supported mapping to cover exotic Modbus data point implementations *)
This mapping combination is not allowed and does not make sense
*) Some MODBUS device manufacturers use, for example, (writable!) holding registers for all types of data points, even for physical inputs, neglecting the existence of input registers (Note: unclear what happens if a holding register is written, which represents a sensor value….)
