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Chapter V Basic Operation Instructions
152
Protocol function:
The main function of Modbus is to read and write parameters. Different function codes
determine different operation requests. The drive Modbus protocol supports the following function
code operations:
Function
code
Function code significance
0x03
Read drive function code parameter and running status parameter
0x06
Rewrite function code or control parameter of single drive
0x10
Rewrite function code or control parameter of multiple drives
The function code parameter, control parameter and status parameter of the drive are mapped
as Modbus read-write registers. The read-write characteristics and range of the function code
parameters follow the instructions in the drive user manual. The group number of the drive function
code is mapped to the high byte address of the register, and the index in the group is mapped to the
low byte address of the register. The control parameter of the drive is virtualized to the drive
function code group 18, and the status parameter of the drive is virtualized to the drive function
code group 19. The correspondence between the function code group number and the high byte of
its mapped register address is as follows:
Group F0: 0x00; group F1: 0x01; group F2: 0x02; group F3: 0x03; group F4: 0x04; group F5:
0x05; group F6: 0x06; group F7: 0x07; group F8: 0x08; group F9: 0x09; FA group: 0x0A; Fb
group: 0x0B; FC group: 0x0C; Fd group: 0x0D; FE group: 0x0E; FF group: 0x0F; U0 group: 0x10;
U1 group: 0x11; drive control parameter group: 0x12; drive status parameter group: 0x13.
For example, the register address of the drive function code parameter F3.02 is 0x0302, and
the register address of the drive function code parameter FE.01 is 0x0E01.
If the operation request fails, the response is an error code and an exception code. The error
code is equal to (function code + 0x80), and the exception code indicates the error reason. The
exception code is listed as follows:
Exception
code
Exception code significance
0x1
Illegal function code.
0x2
Illegal register address.
0x3
Data error, that is, the data exceeds the upper or lower limit.
0x4
Slave operation failed (including errors caused by invalid data, although the
data is within the upper and lower limits).
0x18
Information frame error: Including information length error and check error.
0x20
Parameters cannot be modified.
0x21
Out of the range of function group.
The drive control parameters can complete functions to start, stop, and set running frequency
of the drive. By searching drive status parameters, parameters such as operating frequency, output