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FLOAT32 (32-bit IEEE-754 Float)

A 32-bit IEEE-754 floating-point number stored across two consecutive registers.

Definition

FLOAT32 is the most common way to transmit real-world measurements over Modbus — temperature in degrees, voltage, current, power, flow rate. It follows the IEEE-754 single-precision standard. Two consecutive 16-bit registers hold the 4 bytes of the float, but the byte order varies by manufacturer. Always check the datasheet for byte order (AB-CD, CD-AB, BA-DC, DC-BA).

Quick Facts

Precision~7 decimal digits
Range±1.18×10⁻³⁸ to ±3.4×10³⁸
Size2 registers (4 bytes)
Common orderAB-CD (big-endian) or CD-AB (word-swap)

Example

200.0 in different byte orders across registers 10–11:
AB-CD (big-endian):   4348 0000  → reg10=0x4348, reg11=0x0000
CD-AB (word-swap):    0000 4348  → reg10=0x0000, reg11=0x4348
BA-DC:                4843 0000  → reg10=0x4843, reg11=0x0000
DC-BA (little-end):   0000 4843  → reg10=0x0000, reg11=0x4843

Related Terms

Try it in ModPackQT

See FLOAT32 (32-bit IEEE-754 Float) in action — poll registers, write values, and explore function codes in a free browser-based Modbus tool.

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ModPackQT Modbus Glossary · Updated 2026