smartDEN IP-16R-XX User Manual
13 Apr 2021
10.2.1.3. Read Holding Registers
This command is used to read the contents of a contiguous block of registers.
Request
The Read Holding Registers request specifies the starting register address and
the number of registers to be read.
Note: If the sum of the start address and number of registers exceeds the size of
the accessed block of registers, an error response will be returned.
Request example: Read Week Schedule Start Date fields:
Table 10.21. Read Holding Registers request
Starting Register Address
Response
The Read Holding Registers response returns the function code, byte count, and
register‟s values packed as two bytes per register.
Response example: Read Week Schedule Start Date fields:
Table 10.22. Read Holding Registers response
Error
The possible error responses for function code 0x03 are:
Function Code (1 byte): 0x83 (0x80 + 0x03)
Exception Codes (1 byte):
- 0x01 – Function code not supported
- 0x02 – Incorrect combination of start address and number of registers
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