Delta ASDA-A3 Series User Manual page 869

Modbus Communication
Communication data structure
Definitions for the data frames in the two modes are as follows:
9
ASCII mode:
Start
Slave Address
Function
Data (n-1)
.......
Data (0)
LRC
End 1
End 0
In ASCII communication mode, the message starts with a colon ‟:" (ASCII code: 3AH). The ADR
consists of 2 ASCII codes. The message ends with CR (Carriage Return) and LF (Line Feed).
The codes for data such as communication address, function code, data content, and LRC
(Longitudinal Redundancy Check) are between the start character and the end code.
RTU mode:
Start
Slave Address
Function
Data (n-1)
.......
Data (0)
CRC
End 1
In RTU communication mode, the message starts and ends with silent intervals. The codes for
data such as communication address, function code, data content, and CRC (Cyclical
Redundancy Check) are between the start and end intervals.
9-6
Start character ‟:" (3AH)
Communication address: 1 byte consists of 2 ASCII codes (ADR)
Function code: 1 byte consists of 2 ASCII codes (CMD)
Data content: n-word = 2n-byte consists of 4n ASCII codes, 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 bytes
A silent interval of more than 10 ms
ASDA-A3