Modbus Communication Protocol - Delta ASD-A2-0121 Series User Manual

ASDA-A2
9.3

MODBUS Communication Protocol

There are two modes of MODBUS networks communication, ASCII (American Standard Code for
information interchange) mode and RTU (Remote Terminal Unit) mode. Users could set the
needed communication protocol via parameter P3-02. Apart from these two communication modes,
this servo drive also supports functions of 03H to access more than one data, 06H to write one
character, and 10H to write multiple characters. Please refer to the following descriptions.

Code Description
ASCII Mode:
The so-called ASCII mode is using American Standard Code for Information Interchange (ASCII) to
transmit the data. If desiring to transmit data 64H between two stations (Master and Slave), the
master will send '6' represented by 36H of ASCII code and '4' represented by 34H of ASCII code.
ASCII code of digits 0 to 9 and characters A to F is as follows:
Character '0'
ASCII code 30H
Character '8'
ASCII code 38H
RTU Mode:
Every 8-bit of data is constituted by two 4-bits hexadecimal characters. If data 64H is transmitted
between two stations, it will be transmitted directly, which is more efficient than ASCII mode.
9-6
'1' '2' '3'
31H 32H 33H
'9' 'A' 'B'
39H 41H 42H
'4' '5' '6'
34H 35H 36H
'C' 'D' 'E'
43H 44H 45H
Chapter 9 Communications
'7'
37H
'F'
46H