1 Modbus RTU Protocol
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1.4 Read input registers (Func 04–04H)
Read the Binary data of Input Registers (3X reference) in Slave device.
(1) Query (Master)
Slave address
Function
1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte
(2) Response (Slave)
Slave address
Function
Byte count
Data Data Data Error check (CRC16)
1Byte 1Byte 1Byte 1Byte 1Byte
1Byte
1Byte
1Byte 1Byte
1Byte 1Byte
If read the 2 values within the range from Input Register 300001 (0000 H) to 300002 (0001 H) on
Slave (Address 17) from Master.
Query (Master)
Slave address
Function
11 H 04 H 00 H 00 H 00 H 02 H ## H ## H
If the values of 300001 (0000 H) and 300002 (0001 H) on Slave are respectively “10 (A H)” and
“20 (14 H)”.
Response (Slave)
Slave address
Function Byte count
Data Data Error check (CRC16)
11 H 04 H 04 H 00 H 0A H 00 H 14 H ## H ## H