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C400 Series Operating Manual
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The following illustrates the request frame and response frame with the read and hold register 108-110 as an example. (The contents of
register 108 are read-only, with two-byte values of 0X022B, and the contents of register 109-110 are 0X0000 and 0X0064)
Request Frame Response Frame
Number Systems (Hexadecimal) Function code (Hexadecimal)
Function code 0x03 Register Value (High Bytes) (108) 0x03
Start address (high byte) 0x00 Register Value (Low Bytes)(108) 0x06
Start address (low byte) 0x6B Register Value (High Bytes) (109) 0x02
Number of Read Registers (High Bytes) 0x00 Register Value (Low Bytes) (109) 0x2B
Number of Read Registers (Low Bytes) 0x00 Register Value (High Bytes)(110) 0x00
Register Value (High Bytes)(110) 0x00
Register Value (Low Bytes) (110) 0x00
Function code 0x64
Figure 10: Examples of read and hold register request and response frames
MODBUS function code 0x10: write multiple registers
This function code is used to write continuous registers to remote devices (1... 123 registers) block that specifies the value of the registers
written in the request data frame. Data is packaged in two bytes per register. Response frame return function code, start address and
number of registers written.
Request:
Function Code 1 byte 0x03
Start Address 2 bytes 0x0000….0xfffff
Number of Input Registers 2 bytes 1...125
Number of Bytes 1 byte Nx2
Register Values N×2 bytes Value
N = Register number
Figure 11: Write multiple register request frames
Response:
Function Code 1 byte 0x03
Start Address 2 bytes 0x0000….0xfffff
Number of Input Registers 2 bytes 1...125
Number of Bytes 1 byte Nx2
Register Values N×2 bytes Value
N = Register number
Figure 12: Write multiple register response frames