Autonics SPR3 Series - Modbus RTU: Read Holding Registers (Func 03-03 H)

1 Modbus RTU Protocol
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1.3 Read holding registers (Func 03–03H)
Read 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)
High
Low
High
Low
Low
High
1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte 1Byte
(2) Response (Slave)
Slave address Function Byte count
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
If read the 2 values 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)
High
Low
High
Low
Low
High
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 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