Autonics krn100 series, User Manual

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1 Modbus RTU protocol
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1.3 Read Holding Registers(Func03–03H)
Reads the binary data of Holding Registers(4X reference) in the Slave device.
(1)
Query(Master)
Slave Address
Function
(Command) Starting Address No. of Points(Number of data) Error Check(CRC16)
High Low High Low Low High
1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte
(2) Response(Slave)
Slave Address
Function
(Command)
Byte Count
(Number of
data byte) Data Data Data Error Check(CRC16)
High Low High Low High Low Low High
1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte
The below example is to read 2EA value within Holding Register 40001(0000 H) to 40002(0001
H) on the Slave(Address 17) from the Master.

Query(Master)
Slave Address
Function
(Command) Starting Address No. of Points(Number of data) Error Check(CRC16)
High Low High Low Low High
11 H 03 H 00 H 00 H 00 H 02 H ## H ## H
The below example is when 40001(0000 H) value on the Slave is “555(22B H)” and 40002(0001
H) value is “100 (64 H)”.

Response(Slave)
Slave Address
Function
(Command)
Byte Count
(Number of
data byte) Data Data Error Check(CRC16)
High Low High Low Low High
11 H 03 H 04 H 02 H 2B H 00 H 64 H ## H ## H
CRC16
CRC16