User Manual

Communication
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11.6 Data types and registers
The Modbus specifications does not include requirements on how various data types are to
be displayed on the respective register.
The specification only defines that the register has to be represented as “big endian”. This
means that the high byte of a register is sent first, followed by the low byte.
8-bit integer types:
Example: Value = 1 (0x01)
16-bit integer types:
Example: Value = 4660 (0x1234)
32-bit integer types:
Example: Value = 305419896 (0x12345678)
32-bit IEE 754 floating point:
Example: Value = 123.456 (0x42F6E979)
Table 11-7 8-bit integer types
Register address Register contents (hex)
n 0x0001
Table 11-8 16-bit integer types
Register address Register contents (hex)
n 0x1234
Table 11-9 32-bit integer types
Register address Register contents (hex)
n 0x5678
n +1 0x1234
Table 11-10 32-bit IEE 754 floating point
Register address Register contents (hex)
n 0xE979
n +1 0x42F6