Modbus Interface; Supported Modbus Function Codes; 0X01) Read Coils - Hitachi HX-RIO3 Series User Manual

21

7 Modbus Interface

7.1 Supported Modbus Function Codes

Function Code Function
1(0x01) Read Coils
2(0x02) Read Discrete Inputs
3(0x03) Read Holding Registers
4(0x04) Read Input Registers
5(0x05) Write Single Coil
6(0x06) Write Single Register
8(0x08) Diagnostics
15(0x0F) Write Multiple Coils
16(0x10) Write Multiple registers
23(0x17) Read/Write Multiple registers

7.1.1 1 (0x01) Read Coils

This function code is used to read from 1 to 2000 contiguous status of coils in a remote device. The Request
PDU specifies the starting address, e.g., the address of the first coil specified, and the number of coils. In the
PDU Coils are addressed starting at zero. Therefore, coils numbered 1-16 are addressed as 0-15. The coils in
the response message are packed as one coil per bit of the data field. Status is indicated as 1= ON and 0=
OFF.
Request
Field name
Function Code
Starting Address Hi
Starting Address Lo
Quantity of Outputs Hi
Quantity of Outputs Lo
Response
Field name
Function Code
Byte Count
Output Status
Output Status
In case of address 0x1015~0x1000 output bit value: 10101010_01010101
Description
Read output bit
Read input bit
Read output word
Read input word
Write one bit output
Write one word output
Read diagnostic register
Write a number of output bits
Write a number of output words
Read a number of input words /Write a number of
output words
Example
0x01
0x10
0x00
0x00
0x0A
Example
0x01
0x02
0x55
0x02
HX-RIO3 Series