Schneider Electric VW3 A3 303 用户手册

8. 2. Modes

b RTU mode

The Modbus RTU frame contains no message header byte, nor end of message bytes.
It is defined as follows:

The data is transmitted in binary code.
CRC16: Cyclic redundancy check parameter.
The end of the frame is detected on a silence greater than or equal to 3.5 characters.
The format used for the frames in the rest of this document is RTU mode.

b ASCII mode

The structure of the Modbus ASCII frame is as follows:

Header: By default, ":" = 16#3A. Two other characters are possible: "CR" = 16#0D and "LF" = 16#0A.

LRC: The 2's-complement of the modulo 256 sum (in hexadecimal format) of the frame (excluding the header and end characters) before
ASCII coding.

Example: Write a value of 10 to logic address word 9001 (16#2329) on slave 2

Identical request and response:

In hexadecimal format

In ASCII format

Slave address

Function code

Data

CRC16

Header

":"

Slave

address

Function

code

Data

LRC

End

"CR"

"LF"