ASDA-A2 Chapter 9 Communications
9-8 Revision February, 2017
Communication Data Structure
ASCII Mode:
Start Start character ’: ’ (3AH)
Slave Address Communication address: 1-byte consists of 2 ASCII codes
Function Function code: 1-byte consists of 2 ASCII codes
Data (n-1)
Data content: n-word = 2n-byte includes 4n of ASCII code, n<=10
…….
Data (0)
LRC Error checking: 1-byte consists of 2 ASCII codes
End 1 End code 1: (0DH)(CR)
End 0 End code 0: (0AH)(LF)
The start character of communication in ASCII mode is colon ‘：’ (ASCII is 3AH), ADR is the ASCII
code of two characters. The end code is CR (Carriage Return) and LF (Line Feed). And the
communication address, function code, data content, error checking LRC (Longitudinal
Redundancy Check), etc are between the start character and end code.
RTU Mode:
Start A silent interval of more than 10ms
Slave Address Communication address: 1-byte
Function Function code: 1-byte
Data (n-1)
Data content
：
n-word =2n-byte
，
n<=10
…….
Data (0)
CRC Error checking: 2-byte
End 1 A silent interval of more than 10ms
The start of communication in RTU (Remote Terminal Unit) mode is a silent interval. The end of it
is another silent interval. The communication address, function code, data content, error checking
CRC (Cyclical Redundancy Check), etc are between the start and the end.
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