Delta ASD-B2-0121-F, User Manual

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Communications ASDA-B2-F
8-6
September, 2015
8
RTU Mode:
Start A silent interval of more than 10 ms
Slave Address Communication address: 1 byte
Function Function code: 1 byte
Data (n-1)
Data content: n word = n x 2 byte (n<=10) …….
Data (0)
CRC Error checking: 1 byte
End 1 A silent interval of more than 10 ms
The start and the end of the communication in RTU (Remote Terminal Unit) mode are silent
intervals. The communication address, function code, data content and error checking CRC
(Cyclical Redundancy Check), etc. are between the start and the end.
Example 1: function code 03H, accessing multiple words:
The master issues command to the 1
st
slave and reads continuous 2 words starting from the start
data address 0200H. In response message from the slave, the content of start data address
0200H is 00B1H, and the content of the 2
nd
data address is 1F40H. The maximum allowable data
in one single access is 10. The calculation of LRC and CRC will be described in the following
section.
ASCII Mode:
Command Message (Master): Response Message (Slave):
Start ‘ : ’ Start ‘ : ’
Slave Address
‘0’
Slave Address
‘0’
‘1’ ‘1’
Function
‘0’
Function
‘0’
‘3’ ‘3’
Start Data Address
‘0’
Data Number
(in byte)
‘0’
‘2’ ‘4'
‘0’
Content of Start Data
Address 0200H
‘0’
‘0’ ‘0’
Data Number
(in word)
‘0’ ‘B’
‘0’ ‘1’
‘0’
Content of Second Data
Address 0201H
‘1’
‘2’ ‘F’
LRC Check
‘F’ ‘4’
‘8’ ‘0’
End 1 (0DH)(CR)
LRC Check
‘E’
End 0 (0AH)(LF) ‘8’
End 1 (0DH)(CR)
End 0 (0AH)(LF)