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The following is an example of a function 03 call for data at memory location 03. The
value returned by the instrument is the hex value 1E.
Address
01
Address
01
Note that all the values are interpreted as hexadecimal values. The CRC calculation is
based on the A001 polynomial for RTU Modbus. The function 04 command structure is
similar to the 03 structure.
The following is an example of a function 06 call to change data in register 01 to 200. The
response from the instrument confirms the new value as being set.
Address
01
Address
01
The Transmitter will respond to several error conditions. The three exception codes that
will generate a response from the instrument are:
01 – Illegal Function
02 - Illegal Data Address
03 – Illegal Data Value
04 – Slave Device Failure
The response from the Transmitter with an exception code will have the most significant
bit of the requested function set followed by the exception code and the high and low CRC
bytes.
11/14/2006
Transmit from Host or Master
Cmd
Reg
Reg
HI
LO
03
00
03
Response from Transmitter
Cmd
Byte
Byte
Count
Count
HI
LO
03
00
02
Transmit from Host or Master
Cmd Reg
Reg
HI
LO
06
00
01
Response from Transmitter
Cmd
Reg
Reg
HI
LO
06
00
01
Page 11 of 23
Count
Count
CRC
HI
LO
HI
00
01
74
Data
Data
CRC
HI
LO
HI
00
1E
Data
Data
CRC
HI
LO
HI
00
C8
D9
Data
Data
CRC
HI
LO
HI
00
C8
D9
CRC
LO
0A
CRC
Lo
38
4C
CRC
LO
9C
CRC
LO
9C
Rev. 14
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