Model FL3102
28
7.3 MODBUS Read Status Protocol (Query/Response)
7.3.1 MODBUS Read Query Message
Byte
MODBUS
Range
Referenced to FL3102
1
st
Slave
Address
1-247 *
FL3102 ID (Address)
2
nd
Function
Code
03
Read Holding Registers
3
rd
Starting
Address Hi**
00
Not Used by FL3102
4
th
Starting
Address Lo**
00-FF (Hex)
FL3102 Command Registers
5
th
No.
of
Registers Hi
00
Not Used by FL3102
6
th
No. of
Registers Lo
01
No. of 16 Bit Registers
7
th
CRC Lo
00-FF (Hex)
CRC Lo Byte
8
th
CRC Hi
00-FF (Hex)
CRC Hi Byte
Figure 33 MODBUS Query Messages
NOTE*-
Address 0 is reserved for broadcast mode and will not be supported at
this time.
NOTE**-
Start Address can be a maximum of 9999 Address Locations (0000-
270E)
7.3.2 MODBUS Read Response Message
Byte
MODBUS
Range
Referenced to FL3100, FL31001
1
st
Slave
Address
1-247* (Decimal)
FL3102 ID (Address)
2
nd
Function
Code
03
Read Holding Registers
3
rd
Byte Count
02
No. of Data Bytes
4
th
Data Hi
00-FF (Hex)
FL3102 Hi Byte Status Data
5
th
Data Lo
00-FF (Hex)
FL3102 Lo Byte Status Data
6
th
CRC Lo
00-FF (Hex)
CRC Lo Byte
7
th
CRC Hi
00-FF (Hex)
CRC Hi Byte
Figure 34 MODBUS Read Response Messages
NOTE -
Address 0 is reserved for broadcast mode and will not be supported at
this time.