Longrun LRF-3000P, User Manual

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LRF-3000P Ultrasonic flowmeter
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8.3.2. MODBUS-I Communication Protocol
MODBUS-I protocol applies RTU transmission mode, and its check code applies CRC-16-IBM (multinomial is
X16+X15+X2 + 1, mask code is 0xA001), which is gained through the cyclic redundancy algorithm.
MODBUS-I RTU mode applies the hexadecimal system to transmit data.
1. MODBUS-I protocol function code and format
Function code Function data indicated
0x03 Read register
0x06 Single write register
2. Use of MODBUS protocol function code 0x03
Information frame format of the read register sent by the host:
Slave address
Operation function
code
Register’s first
address
Number of registers Check code
1 byte 1 byte 2 bytes 2 bytes 2 bytes
0x01~ 0xF7 0x03 0x0000 ~ 0xFFFF X0000 ~ 0x7D CRC Check code
Slave feedback data frame format:
Slave address
Read operation
function code
Number of data
bytes
Data Check code
1 byte 1 byte 1 byte N*x2 bytes 2 bytes
0x01~ 0xF7 0x03 2xN* N*x2 data CRC Check code
N* =Number of data registers.
3. MODBUS protocol function code 0x06
Information frame format of the write-in single register sent by the host (function code 0
x 06):
Slave address
Operation function
code
Register’s first
address
Number of registers Check code
1 byte 1 byte 2 bytes 2 bytes 2 bytes
0x01~0xF7 0x06 0x0000~0xFFFF X0000 ~ 0xFFFF CRC Check code
Slave feedback data frame format (function code 0x06):
Slave address
Operation function
code
Register’s first
address
Number of registers Check code
1 byte 1 byte 2 bytes 2 bytes 2 bytes
0x01~0xF7 0x06 0x0000~0xFFFF X0000~0xFFFF CRC Check code
Flowmeter’s address