0X02) Read Discrete Inputs; 0X03) Read Holding Registers - Hitachi HX-RIO3 Series User Manual

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7.1.2 2 (0x02) Read Discrete Inputs

This function code is used to read from 1 to 2000 contiguous status of discrete inputs in a remote device. The
Request PDU specifies the starting address, e.g., the address of the first input specified, and the number of
inputs. In the PDU Discrete Inputs are addressed starting at zero. Therefore, Discrete inputs numbered 1-16
are addressed as 0-15. The discrete inputs in the response message are packed as one input per bit of the
data field. Status is indicated as 1= ON; 0= OFF.
Request
Field name
Function Code
Starting Address Hi
Starting Address Lo
Quantity of Inputs Hi
Quantity of Inputs Lo
Response
Field name
Function Code
Byte Count
Input Status
Input Status
In case of address 0x0015~0x0000 input bit value: 00000000_10000000

7.1.3 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
Function Code
Starting Address Hi
Starting Address Lo
Quantity of Register Hi
Quantity of Register Lo
Example
0x02
0x00
0x00
0x00
0x0A
Example
0x02
0x02
0x80
0x00
Example
0x03
0x08
0x00
0x00
0x02
HX-RIO3 Series