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FnIO MODBUS Adapter NA-9189
FnIO S-Series
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6.2.4.
4 (0x04) Read Input Registers
This function code is used to read from 1 to approx. 125 contiguous input 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
0x04
Starting Address Hi
0x00
Starting Address Lo
0x00
Quantity of Register Hi
0x00
Quantity of Register Lo
0x02
Response
Field name
Example
Function Code
0x04
Byte Count
0x04
Input Register #0 Hi
0x00
Input Register #0 Lo
0x80
Input Register #1 Hi
0x00
Input Register #1 Lo
0x00
-
In case of address 0x0000, 0x0001 input register value: 0x0080, 0x0000.