Sierra Instruction Manual InnovaSonic
®
203 Economical
50
d can be set in Menu 46. Numbers 13, 10, 42, and 38 are reserved and cannot be used.
9.4 Modbus-RTU Communication Protocol
This Modbus-I Protocol uses RTU transmission mode. The Verification Code uses CRC-16-IBM (polynomial is
X
16
+X
15
+X
2
+1, shield character is
0xA001
) which is gained by the cyclic redundancy algorithm method.
Modbus RTU mode uses hexadecimals to transmit data.
1)
Modbus-I Protocol Function Code and Format
The flow meter protocol supports the following two-function codes of the Modbus:
Function Code
Performance data
0x03
Read register
0x06
Write single register
2)
Modbus Protocol function code 0x03 usage
The host sends out the read register information frame format:
Slave Address
Operation Function
Code
First Address Register
Register Number
Verify Code
1 byte
1 byte
2 bytes
2 bytes
2 bytes
0x01~0xF7
0x03
0x0000~0xFFFF
0x0000~0x7D
CRC(Verify)
The slave returns the data frame format:
Slave Address
Read Operation Function
Code
Number of Data Bytes
Data Bytes
Verify Code
1 byte
1 byte
1 byte
N*x2 byte
2 byte
0x01~0xF7
0x03
2xN*
N*x2
CRC(Verify)
N*
＝
data register number
3)
Modbus Protocol function code 0x06 usage
The host sends a command to write a single register information frame format (performance code 0x06):
Slave Address
Operation Function Code
Register Address
Register Data
Verify Code
1 byte
1 byte
2 bytes
2 bytes
2 bytes
0x01~0xF7
0x06
0x0000~0xFFFF
0x0000~0xFFFF
CRC(Verify)
The slave returns the data frame format (performance code 0x06):
Slave Address
Operation Function Code
Register Address
Register Data
Verify Code
1 byte
1 byte
2 bytes
2 bytes
2 bytes
