Xytronix Research & Design ControlByWeb X317, User Manual

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Operation X-317™ Users Manual
5.3.5 Write Multiple Registers (Modbus Function Code 16 (0x10))
The Write Multiple Registers function is used to write (set) the analog output value(s).
32-bit values are written to 16-bit register pairs. Consequently, addresses and registers must be even
numbers.
5.3.5.1 Request
Modbus TCP Request Frame Example – Write Analog Channel(s)
Field Name Length Function Example Data
(AnalogOut1)
Transaction Identifier 2 bytes Synchronization number. 0x0001
Protocol Identifier 2 bytes Zero for Modbus/TCP 0x0000
Message Length 2 bytes Number of bytes in frame (below) 0x000B
Unit Identifier 1 byte Slave Address (0xff if not used) 0xFF
Function Code 1 byte Write multiple registers 0x10
Start Address 2 bytes Start Address: 0x0510
Quantity of registers 2 bytes Quantity of registers: 0x0002
Byte Count 1 byte Byte count (2 x N) 0x02
Data N * 2 Register(s) value: 0x800042A2
5.3.5.2 Response
Response Frame Example
Field Name Length Function Example Data
Transaction Identifier 2 bytes Synchronization number. 0x0001
Protocol Identifier 2 bytes Zero for Modbus/TCP 0x0000
Message Length 2 bytes Number of bytes in frame (below)
0x0006
Unit Identifier 1 byte Slave Address (0xff if not used) 0xFF
Function Code 1 byte Write multiple registers 0x10
Starting Address 2-bytes Starting address 0x0510
Quantity of registers 2-bytes Quantity of registers 0x0002
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