Chapter 9 Communication ASDA-A2R Series
9-6 Revision December, 2014
Communication Data Structure
The Data Frame in two different communication modes:
ASCII mode:
Start
Start character ’：’ (3AH)
Slave Address Communication address: 1-byte includes 2 ASCII codes
Function Function code: 1-byte includes 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 includes 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 which is longer 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：1-byte
End 1 A silent interval which is longer 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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