Modbus Communication Protocol; Code Description; Ascii Mode; Data Format - Delta ASD-B2-0121-B User Manual

Chapter 8 MODBUS Communications

8.3 MODBUS Communication Protocol

When using RS-232/485 serial communication interface, each ASDA-B2 series AC servo drive
has a pre-assigned communication address specified by parameter "P3-00". The computer
then controls each AC servo drive according to its communication address. ASDA-B2 series AC
servo drive can be set up to communicate on a MODBUS networks using on of the following
modes: ASCII (American Standard Code for Information Interchange) or RTU (Remote Terminal
Unit). Users can select the desired mode along with the serial port communication protocol in
parameter "P3-02".

Code Description:

ASCII Mode:

Each 8-bit data is the combination of two ASCII characters. For example, a 1-byte data: 64 Hex,
shown as '64' in ASCII, consists of '6' (36Hex) and '4' (34Hex).
The following table shows the available hexadecimal characters and their corresponding ASCII
codes.
Character '0'
ASCII code 30H
Character '8'
ASCII code 38H
RTU Mode:
Each 8-bit data is the combination of two 4-bit hexadecimal characters. For example, a 1-byte
data: 64 Hex.

Data Format:

10-bit character frame (For 7-bit character)
7N2
Start
bit
7E1
Start
bit
7O1
Start
bit
8-8
'1' '2'
31H 32H
'9' 'A'
39H 41H
0 1 2
7-data bits
10-bits character frame
0 1 2
7-data bits
10-bits character frame
0 1
2
7-data bits
10-bits character frame
'3' '4' '5'
33H 34H 35H
'B' 'C' 'D'
42H 43H 44H
3 4 5
3 4 5
3 4 5
'6' '7'
36H 37H
'E' 'F'
45H 46H
Stop
Stop
6
bit
bit
Even
Stop
6
parity
bit
Odd
Stop
6
parity
bit
Revision June 2010