A-TS
123
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0x302. The function code parameter PB.01 maps to the register address
0xB01.
As already described the formatting of an entire data frame, the following
will focus on the Modbus protocol function codes and the format and
meaning of the data. It refers to the content of "function code" and "Data"
section in the data frame format. The two parts compose a Modbus
application layer protocol data unit. The application-layer protocol data
unit mentioned below refers to these two parts.
The application layer protocol data unit for reading inverter parameters
is as follows:
Application layer protocol Data
Unit
Data length
( number of
bytes )
Values or range
Function code
1
0x03
Initial register address
2
0x0000~0xFFFF
Register number
2
0x0001~0x0004
Response format as below:
Application layer protocol
Data Unit
Data length
( number of bytes )
Values or range
Function code
1
0x03
Read number of bytes
1
2* Register number
Read content
2* Register
number
If the operation fails, error code and exception code will be responded.
The error code is “function code + 0x80”, exception code denotes the
cause of the error. Exception code listed below:
exception
code
Description
0x1
Illegal function code
0x2
Illegal register address.
0x3
Data error, i.e., data more than upper limit or lower limit.
0x4
Operation failure of slave drive ( including error caused by invalid
data in the range of upper limit and lower limit )
