Communication Data Structure - Delta ASDA-A3 Series User Manual

MODBUS Communication

Communication data structure

Definitions for the data frames in the two modes are as follows:
ASCII mode:
9
Slave Address
Function
Data (n-1)
Data (0)
End 1
End 0
The start character in ASCII communication mode is the colon ‟:" (ASCII code: 3AH). The ADR is
two characters in ASCII code. The end code is CR (Carriage Return) and LF (Line Feed). The
codes for data such as communication address, function code, data content and error checking
(LRC: Longitudinal Redundancy Check)), are between the start character and the end code.
RTU mode:
Slave Address
Function
Data (n-1)
Data (0)
End 1
The start and end of the communication in RTU mode are silent intervals. The codes for data
such as communication address, function code, data content and error checking code (CRC
(Cyclical Redundancy Check)), are between the start interval and the end interval.
9-6
Start 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 consists of n x 4 ASCII codes, n ≤ 10
LRC Error check: 1 byte consists of 2 ASCII codes
End code 1: (0DH) (CR)
End code 0: (0AH) (LF)
Start A silent interval of more than 10 ms
Communication address: 1 byte
Function code: 1 byte
....... Data content: n-word = 2n-byte, n ≤ 10
CRC Error check: 1 byte
A silent interval of more than 10 ms
ASDA-A3
Revision December, 2017