Autonics BFC Series, User Manual

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1 Modbus RTU protocol
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1.3 Read Holding Registers(Func 03–03H)
Reads the Binary data of Holding Registers(4X 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(Data) Data(Data) Error Check(CRC16)
Hi(Upper) Lo(Lower) Hi(Upper) Lo(Lower) Hi(Upper) Lo(Lower) Lo(Lower) Hi(Upper)
1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte
If reading the values of 2, from Holding Register 400001(0000 H) to 400002(0001 H), in
Slave(Address 17) from the 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 03 H 00 H 00 H 00 H 02 H ## H ## H
If the value of 400001(0000 H) on Slave is “555(22B H)” and the value of 400002(0001 H) is
“100(64 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 03 H 04 H 02 H 2B H 00 H 64 H ## H ## H
CRC16
CRC16