Autonics krn100 series, User Manual

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2 Modbus TCP protocol
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2.3 Read Holding Registers(Func03–03H)
Reads the binary data of Holding Registers(4X reference) in the Slave device.
(1)
Query(Master)
MBAP Header
Function
(Command) Starting Address No. of Points(Number of data
)
High Low High Low
7Byte 1Byte 1Byte 1Byte 1Byte 1Byte
(2)
Response(Slave)
MBAP Header
Function
(Command)
Byte Count
(Number of data
byte) Data Data Data
High Low High Low High Low
7Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte
The below example is to read 2EA value within Holding Register 400001(0000 H) to
400002(0001 H) on the Slave from the Master.

Query(Master)
MBAP Header
Function
(Command)
Starting Address No. of Points(Number of data)
High Low High Low
00 0a 00 00 00 06 01H 03 H 00 H 00 H 00 H 02 H
The below example is when 400001(0000 H) value on the Slave is “555(22B H)” and
400002(0001 H) value is “100 (64 H)”.

Response(Slave)
MBAP Header
Function
(Command)
Byte Count
(Number of data
byte) Data Data
High Low High Low
00 0a 00 00 00 07 01H 03 H 04 H 02 H 2B H 00 H 64 H