Instruction Manual

5. Modbus RTU
64
Modbus
(3) Query format
In a query message, specify the address of the register from which to start reading data, and
number of bytes in registers to be read.
1 register (1 address) = 2 bytes = 16-bit data
Field RTU mode
8-bit data
Number of data items
(number of bytes)
Remarks
Start None Silent interval
Slave address [H] Arbitrary 1 Axis No. + 1 (01
H
to 10
H
)
Function code [H] 03 1 Register reading code
Start address [H] Arbitrary 2 Refer to 5.3.1 (2),
”Start address list”
Number of registers [H] Arbitrary 2 Refer to the start address
list.
Error check [H] CRC (16 bits) 2
End None Silent interval
Total number of bytes 8
(4) Response format
Field RTU mode
8-bit data
Number of data items
(number of bytes)
Remarks
Start Silent interval
Slave address [H] Arbitrary 1 Axis No. + 1 (01
H
to 10
H
)
Function code [H] 03 1 Register reading code
Number of data bytes [H] 1 Total number of bytes of
registers specified in the
query
Data 1 [H] Number of bytes of
register specified in the
query
Data 2 [H] Number of bytes of
register specified in the
query
Data 3 [H] Number of bytes of
register specified in the
query
Data 4 [H] Number of bytes of
register specified in the
query
: :
: :
Error check [H] CRC (16 bits) 2 Silent interval
End None
Total number of bytes 256 max.