Delta ASD-A2-0121 Series User Manual page 603

ASDA-A2
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Communication Data Structure
Definitions for the data frames in the two modes are as follows:
ASCII Mode:
Start
Slave Address
Function
Data (n-1)
.......
Data (0)
LRC
End 1
End 0
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
Slave Address
Function
Data (n-1)
.......
Data (0)
CRC
End 1
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.
9-8
Start character ': ' (3AH)
Communication address: 1-byte consists of 2 ASCII codes
Function code: 1-byte consists of 2 ASCII codes
Data content: n-word = 2n-byte includes 4n of ASCII code, n<=10
Error checking: 1-byte consists of 2 ASCII codes
End code 1: (0DH)(CR)
End code 0: (0AH)(LF)
A silent interval of more than 10 ms
Communication address: 1-byte
Function code: 1-byte
Data content ： n-word =2n-byte ， n<=10
Error checking: 2-byte
A silent interval of more than 10 ms
Chapter 9 Communications