Modbus RTU Protocol

Communications format

bit order: lsb first

byte order: big endian

Data bits:8

Parity: None

Stop bits: 1

Floating point number follows IEEE754-1985. The float32 below stands for 32bits Single precision floating point number.

Terminology

‌‌Register: Length of 2 Byte or 16bit which is unit length of memory in Modbus RTU.

‌Byte: 8 bit length

Definition and function of memory

Modbus Memory Access

Modbus-accessible memory is divided into two main categories: read-only and read/write.

• The read-only memory primarily contains data related to the flow meter’s operational status, such as instantaneous flow rate. This category is the most commonly accessed memory area. Read-only memory can only be accessed using Function Code 04 (Read Input Registers).

Relevant register mappings and details can be found on the following page: