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2. Use of the MODBUS protocol function code 0x03
The host sends out the frame format of the read register information:
Slave address
function code
1 byte
0x01 ~ 0xF7
The slave returns the data frame format:
Slave address
1 byte
0x01 - 0xF7
N*= Data register number
3. Use of the MODBUS protocol function code 0x06
The host sends a command to write a single register information frame format (function code
0x06):
Slave address
function code
1 byte
0x01 - 0xF7
The slave returns the data frame format (function code 0x06):
Slave address
function code
1 byte
0x01 - 0xF7
The range of flow meter addresses is 1 ... 247 (hexadecimal: 0x01 - 0xF7) and can be checked
in menu 46. For example, the decimal number "11" displayed in menu 46 means that the flow
meter address in the MODBUS protocol is 0x0B.
The CRC verification code adopts CRC-16-IBM (polynomial is X16+X15+X2+1, shield character
is 0xA001) gained by the cyclic redundancy algorithm method. The low byte of the verification
code is at the beginning, while the high byte is at the end.
For example, to read the address 1 (0x01) in RTU mode if the instantaneous flow rate uses hour
(
),
3
as unit
m
/h
that is, i. e. reads 40005 and 40006 register data, the read command is as follows:
0x01
Flowmeter
Address
Operation
First address
1 byte
0x03
Read
Number of
operation
data bytes
function code
1 byte
0x03
Operation
1 byte
0x06
Operation
1 byte
0x06
0x03
0x00 0x04
Function Code
First
Register
© PCE Instruments
Register
register
number
2 bytes
2 bytes
0x0000 -
0x0000 - 0x7D
0xFFFF
Data bytes
1 byte
N*x2 byte
2xN*
N*x2 ( Data )
Register
Register data
address
2 bytes
2 bytes
0x0000 -
0x0000 -
0xFFFF
0xFFFF
Register
Register data
address
2 bytes
2 bytes
0x0000 -
0x0000 -
0xFFFF
0xFFFF
0x00 0x02
Address
Register
Numbers
40
Verify code
2 bytes
CRC (Verify )
Verify code
2 bytes
CRC ( Verify )
Verify code
2 bytes
CRC ( Verify )
Verify code
2 bytes
CRC ( Verify )
0x85 0xCA
CRC
Verify
Code
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