TFM VT-222 Vortex Flowmeter User Manual
1 Protocol Overview
TFM VT-222 Multivariable Vortex Flowmeter communication protocol using MODBUS-RTU mode.
●
Communication interface
:
RS-485.
●
Support standard Modbus-RTU
:
Support functions codes
03, 04, 06, 16.
●
Register length limit
:
S
upports max 8 registers.
1.1
Serial Communication Parameters
Parameter
Ranges
Default Value
Address
1-247
1
Baud rate
9600, 4800, 2400, 1200, 600
9600
Data Length
8
8
Parity
None
None
Stop Bits
1
1
1.2
Communication DataFormat
TFM VT-222 supports the following data format types:
1) Float
:
Floating point data
The float data is a 4-byte floating-point number in standard IEEE-754 in the ABCD byte format.
For example, in the case of 100.0 (hexadecimal representation: 0x42, 0xC8, 0x00, 0x00), the order
of transmission is: 0x42, 0xC8, 0x00, 0x00. 100 is 42C80000 in IEEE 754 ABCD float
2)
U-16
:
2-byte 16 bit unsigned integer
For example, in the case of 4660 (hexadecimal representation: 0x12, 0x34), the order of
transmission is: 0x12, 0x34 in the AB format.
3)
U-8
:
Single-byte unsigned 8 bit number
1.3
Communication Interface Functions Format
1.3.1
Function
03 (Read Holding Registers)
Example: Read the Full Scale value (assuming the current value is 100.0), the corresponding
register starting address: 8204 (0x200C in hexadecimal). Note: 100 is 42C80000 in IEEE 754
ABCD float
Request frame:
Address
Function Code
Register Address
Register count
CRC Check
0x01
0x03
0x20,0x0C
0x00,0x02
0x05,0xB0
The correct response frame
:
TFM VT-222 Vortex Flowmeter Quick Manual Rev 10f page 21 of 30