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4
MODBUS STANDARD FUNCTIONS
(ASCII mode)
Function code
Function code
0
1
(30
)
(31
)
H
H
(L)
(H)
4
- 17
4.3 Protocol Data Unit Formats by Functions
(b) Frame mode of the message format
The message formats in Section 4.4 to 4.20 are based on the case in the RTU
mode.
For use in ASCII mode, convert the values into ASCII codes.
(Conversion example)
(RTU mode)
Function code
Function
Head coil number
code
(006E
(01
)
H
(H)
Data
Head coil number
0
0
6
(30
)
(30
)
(36
H
H
(H)
Figure 4.8 Conversion example from RTU mode to ASCII mode
(c) Response message format
The response message formats issued from the slave to the master differs
depending on whether the slave has normally completed or failed to handle the
requested processing (read/write, diagnostics, etc.)
The formats for normal and error completions are shown in Section 4.4 to 4.20.
Data
Read points
)
(003F
H
H
(L)
(H)
Convert RTU mode to ASCII mode
E
0
)
(45
)
(30
)
H
H
H
(L)
(H)
)
(L)
Data
Read points
0
3
(30
)
(33
)
H
H
F
(46
)
H
(L)
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