Autonics BFC Series, User Manual

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1 Modbus RTU protocol
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1.4 Read Input Registers(Func 04–04H)
Reads the Binary data of Input Registers(3X reference) in Slave device.
(1) Query (Master)
Slave Address Function
Starting Address No. of Points Error Check(CRC16)
Hi(Upper) Lo(Lower) Hi(Upper) Lo(Lower) Lo(Lower) Hi(Upper)
1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte
(2) Response (Slave)
Slave Address Function Byte Count Data Data Data
Error Check(CRC16)
Lo(Lower)
Hi(Upper)
1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte
If reading the values of 2 range from Input Register 300001(0000 H) to 300002(0001 H) on
Slave (Address 17) from Master.

Query (Master)
Slave Address Function
Starting Address No. of Points Error Check(CRC16)
Hi(Upper) Lo(Lower) Hi(Upper) Lo(Lower) Lo(Lower) Hi(Upper)
11 H 04 H 00 H 00 H 00 H 02 H ## H ## H
If the values of 300001(0000 H) on Slave is “10(A H)” and the values of 300002(0001 H) on
Slave is “20(14 H)”.

Response (Slave)
Slave Address Function Byte Count
Data(Data) Data(Data) Error Check(CRC16)
Hi(Upper) Lo(Lower) Hi(Upper) Lo(Lower) Lo(Lower) Hi(Upper)
11 H 04 H 04 H 00 H 0A H 00 H 14 H ## H ## H
CRC16
CRC16