GN-9289 User Manual
Page 36 of (70)
G-series GN-9289 Modbus TCP_UDP Rev. 1.01.docx
8.2.3.
3 (0x03) Read Holding Registers
This function code is used to read the contents of a contiguous block of holding registers in a remote device.
The Request PDU specifies the starting register address and the number of registers.
The register data in the response message are packed as two bytes per register, with the binary contents
right justified within each byte. For each register, the first byte contains the high order bits and the second
contains the low order bits.
Request
Field name
Example
Function Code
0x03
Starting Address Hi
0x08
Starting Address Lo
0x00
Quantity of Register Hi
0x00
Quantity of Register Lo
0x02
Response
Field name
Example
Function Code
0x03
Byte Count
0x04
Output Register#0 Hi
0x11
Output Register#0 Lo
0x22
Output Register#1 Hi
0x33
Output Register#1 Lo
0x44
- In case of address 0x0800, 0x0801 output register value: 0x1122, 0x3344.
