Modbus register interpreter
Paste two holding registers and see the value in every word and byte order, so you can tell which one your PLC or meter is using.
Open the calculator in EM·LINKBelow is a worked example. The working calculator runs free in EM·LINK.
Worked example
Example inputs
Example result
This is the only order that falls inside your expected range.
| Order | Bytes | Value |
|---|---|---|
| ABCD | 41 26 66 66 | 10.4 |
| CDAB | 66 66 41 26 | 2.718 × 10²³ |
| BADC | 26 41 66 66 | 6.710 × 10⁻¹⁶ |
| DCBA | 66 66 26 41 | 2.717 × 10²³ |
Also as integers: int16 16678 and 26214, int32 1093035622.
Decoding runs in your browser. Nothing is sent to us.
The working calculator is Modbus Register Interpreter in EM·LINK, our free browser tool. The button opens it directly.
How to read the result
A 32-bit float needs two 16-bit Modbus registers. The protocol only says each register is sent high byte first. It does not say which register comes first, so manufacturers pick different orders. If your master and the device disagree, you get a number that is wildly too big or too small instead of an error.
The quickest check is the expected range. A pressure transmitter will not read 2.718e23 bar, so the order that gives a sensible number is almost always the right one.
How this is calculated
The two registers are split into four bytes, A B C D. Each order rearranges those bytes and reads them as one IEEE 754 single-precision number: 1 sign bit, 8 exponent bits and 23 fraction bits.
The full derivation, step by step, is in the EM·LINK documentation.
Calculated per Modbus Application Protocol Specification V1.1b3 and IEEE 754-2019. These tools are an engineering aid, not a certification.
Next step
Polling more than one device? Embedos Edge reads Modbus and pushes it to the cloud. Book a 20 min commissioning call.
Common questions
Why does my Modbus float read as a tiny or huge number?
The word or byte order in your master does not match how the device packed the value. Check the four decodes and pick the one inside the expected range.
Which word order is most common?
ABCD is the standard, but CDAB (word swapped) is the most frequent mismatch on PLCs and energy meters.
Related tools
- CRC and checksum, to check the frame CRC on a captured Modbus RTU message.
- RS-485 termination and bias, for a line that drops or garbles frames.
- UART baud rate error, when a slave answers only some of the time.