(0X03) Read Holding Registers - Hitachi HX-RIO3 Series User Manual

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A.3.3. 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
Start of Frame
Slave Address
Function Code
Starting Address Hi
Starting Address Lo
Quantity of Register Hi
Quantity of Register Lo
Error Check (CRC/LRC)
End of Frame
•
Response
Field name
Start of Frame
Slave Address
Function Code
Byte Count
Output Register #0 Hi
Output Register #0 Lo
Output Register #1 Hi
Output Register #1 Lo
Error Check (CRC/LRC)
End of Frame
In case of address 0x0800, 0x0801 output register value: 0x1122, 0x3344.
-
Example RTU
- t1-t2-t3
0x07 0x07
0x03 0x03
0x08 0x08
0x00 0x00
0x00 0x00
0x02 0x02
- 0xC6, 0x0D
- t1-t2-t3
Example RTU
- t1-t2-t3
0x07 0x07
0x03 0x03
0x04 0x04
0x11 0x11
0x22 0x22
0x33 0x33
0x44 0x44
- 0x2D, 0xC6
- t1-t2-t3
HX-RIO3 Series