Modbus RTU Protocol

Communication Format

Name	Value	Description
Bit Order	lsb first	Data is transmitted starting from the Least Significant Bit (LSB).
Byte Order	big endian	Data is transmitted starting from the Most Significant Byte (MSB).
Data bits	8	Each character or byte consists of 8 data bits.
Parity	None	No parity bit is used for error checking during transmission.
Stop bits	1	1 stop bit is used at the end of each character.
Floating-Point Standard	IEEE 754-1985	Floating-point numbers (Float32) use the 32-bit single-precision format.
Register	2 Byte / 16 bit	Floating-point numbers (Float32) use the 32-bit single-precision format.
Byte	8 bit	The basic unit length of data transmission.

In Modbus RTU communication, a Register is the basic unit of memory communication, with a length of 2 bytes (16 bits). A Byte is the basic unit of data transmission, with a length of 8 bits.

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Memory Definition and Functions

Memory Types	Read-Only Memory	Read/Write Memory
Main Functions	Read the device’s real-time status and results.	Set the device’s operating parameters and calibration values.
Stored Content	Stores memory related to flow status, such as instantaneous flow and totalized flow.	Stores memory related to flow configuration parameters, such as pipe diameter, calibration coefficients, and flow cutoff values.
Access Rights	Read-only: can only be read, not written.	Read/Write: can be both read and written.
Function Codes	Read Command: 04 (Read Input Registers)	Read Command: 03; Write Command: 06 / 30 / 31