Analog Data Formats

Modbus natively only supports two data formats: single bits, and 16-bit registers. To allow for other data types, Modbus devices often combine multiple 16-bit registers into a single value.

Data formats are only used for input and holding registers. Coils and discrete inputs are always interpreted as single bits.

Xentara supports the following data formats for input and holding registers:

uint16

A single 16-bit register is interpreted as an unsigned 16-bit integer value.

The value 23,456 (5BA0_HEX) will be encoded as as follows:

Register 0: 5BA0

int16

A single 16-bit register is interpreted as an signed 16-bit integer value.

The value -23,456 (A460_HEX) will be encoded as as follows:

Register 0: A460

uint32

Two 16-bit registers are combined to form an unsigned 32-bit integer value using big endian register order (most significant bits first).

The value 123,456,789 (075B CD15_HEX) will be encoded as as follows:

Register 0: 075B

Register 1: CD15

int32

Two 16-bit registers are combined to form a signed 32-bit integer using big endian register order (most significant bits first).

The value -123,456,789 (F8A4 32EB_HEX) will be encoded as follows:

Register 0: F8A4

Register 1: 32EB

uint64

Four 16-bit registers are combined to form an unsigned 32-bit integer using big endian register order (most significant bits first).

The value 1,234,567,890,123,456,789 (1122 10F4 7DE9 8115_HEX) will be encoded as as follows:

Register 0: 1122

Register 1: 10F4

Register 2: 7DE9

Register 3: 8115

int64

Four 16-bit registers are combined to form a signed 32-bit integer using big endian register order (most significant bits first).

The value -1,234,567,890,123,456,789 (EEDD EF0B 8216 7EEB_HEX) will be encoded as as follows:

Register 0: EEDD

Register 1: EF0B

Register 2: 8216

Register 3: 7EEB

uint32LE

Two 16-bit registers are combined to form an unsigned 32-bit integer value using little endian register order (least significant bits first).

The value 123,456,789 (075B CD15_HEX) will be encoded as as follows:

Register 0: CD15

Register 1: 075B

int32LE

Two 16-bit registers are combined to form a signed 32-bit integer using little endian register order (least significant bits first).

The value -123,456,789 (F8A4 32EB_HEX) will be encoded as follows:

Register 0: 32EB

Register 1: F8A4

uint64LE

Four 16-bit registers are combined to form an unsigned 32-bit integer using little endian register order (least significant bits first).

The value 1,234,567,890,123,456,789 (1122 10F4 7DE9 8115_HEX) will be encoded as as follows:

Register 0: 8115

Register 1: 7DE9

Register 2: 10F4

Register 3: 1122

int64LE

Four 16-bit registers are combined to form a signed 32-bit integer using little endian register order (least significant bits first).

The value -1,234,567,890,123,456,789 (EEDD EF0B 8216 7EEB_HEX) will be encoded as as follows:

Register 0: 7EEB

Register 1: 8216

Register 2: EF0B

Register 3: EEDD

floatABCD

Two 16-bit registers are combined to form a 16-bit IEEE single precision floating point value in big endian register order (most significant bits first).

The value 1234.5 (449A 5000_HEX) will be encoded as as follows:

Register 0: 449A

Register 1: 5000

floatCDAB

Two 16-bit registers are combined to form a 16-bit IEEE single precision floating point value in little endian register order (least significant bits first).

The value 1234.5 (449A 5000_HEX) will be encoded as as follows:

Register 0: 5000

Register 1: 449A

floatBADC

Two 16-bit registers are combined to form a 16-bit IEEE single precision floating point value in big endian register order (most significant bits first), but with the bytes swapped within each register.

The value 1234.5 (449A 5000_HEX) will be encoded as as follows:

Register 0: 9A44

Register 1: 0050

floatDCBA

Two 16-bit registers are combined to form a 16-bit IEEE single precision floating point value in little endian register order (least significant bits first), but with the bytes swapped within each register.

The value 1234.5 (449A 5000_HEX) will be encoded as as follows:

Register 0: 0050

Register 1: 9A44