E6581741
8.4. "03 (0x03) Read Holding Registers" function
The Modbus request is used to read the values of a number (No. of Points) of adjacent words starting at the address indicated (Starting Address). The values read are restored one after another, at the end of the response (First Point Data
Request Format:
Byte | Meaning |
0Function Code = 03h
1Starting Address Hi
2Starting Address Lo
3No. of Points Hi (0)
4No. of Points Lo (1 - 125)
Response format:
Byte | Meaning |
0Function Code = 03h
1Byte Count (B = 2 × No. of Points)
2First Point Data Hi
3First Point Data Lo
・・・ | ・・・・・・・・・・・・・・・・ |
BLast Point Data Hi
B+1 Last Point Data Lo
Exception response format:
Byte | Meaning |
0Function Code = 83h Exception Code =
101 (Illegal Function)
02 (Illegal Data Address)
03 (Illegal Data Value)
Notes
If the communication number that doesn't exist is read, the option returns 0x8000.
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