Industrial protocols

Modbus 16-, 32- and 64-bit register decoder

Decode integer and IEEE 754 floating-point values from registers, with the byte layout for the selected order.

Calculate

Registers and interpretation
Use one four-digit word per register, in the order returned by the device.

Worked example

Decoded value

234 

Applied byte layout
ABCD
Bytes presented to the decoder
43 6A 00 00
Value width
2 registers

The decimal text round-trips to the decoded binary value. NaN or infinity may be documented device states, overflow states or the wrong type or order; confirm the register map.

Method and assumptions

Formula

Reorder complete 16-bit registers, optionally swap the two bytes within each register, then decode the selected type

Modbus defines each 16-bit register, but multi-register value layout is device-specific. The device register map must name the data type and order.

Limits of this result

  • The tool does not infer a correct order from a plausible-looking number.
  • NaN and infinity may represent documented invalid, unavailable or overflow states, or an incorrect type/order. Consult the device register map.

Technical sources

  1. MODBUS Application Protocol Specification V1.1b3Modbus Organization · 2012-04-26
  2. TeSys Tera Modbus RTU communication guide — UINT32 frame exampleSchneider Electric · DOCA0355EN-01

Put the value to work

Read the related engineering guidance, or carry this task into System Builder to identify the signal path and EpiSensor products.

Continue in System Builder Read: What Is SCADA?

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