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 is divided into two categories, read-only and read-write.
Read-only type is mainly for flow meter status related memory, such as instantaneous flow rate. This is also the most commonly used memory. Detail information in following page:
Read-only memory read instruction(04) and memory lists
Read-write memory is mainly to set-up parameters such as pipe diameter, and to reset variables, such as set zero on the cumulative flow. Read-write memory is only readable by using instruction 03. You can only change one parameter at a time with the write operation. If the length of the target register is 1, please use instruction 06. If the length is 2 registers, please use instruction 30. Please see read-write memory detail page below:
Read-write memory instruction detail information as below:
Read-write memory read instruction(03)
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