Delta ASD-A3-0121, Руководство пользователя

Страница: 471 / 603

MODBUS Communication ASDA-A3
9-4
Revision December, 2017
9
9.3 MODBUS communication protocol
There are two modes of MODBUS network communication: ASCII (American Standard Code for
Information Interchange) and RTU (Remote Terminal Unit). You can set both communication
protocols (ASCII and RTU) with the P3.002 parameter. The ASDA-A3 servo drive also supports
these functions: accessing data (03H), writing one character (06H) and writing multiple
characters (10H). Please refer to the following descriptions.
Code Description
ASCII mode:
In ASCII mode, data is transmitted in ASCII (American Standard Code for Information
Interchange) format. For instance, when transmitting “64H” between two stations (master and
slave), the master sends
36H to represent ‟6” and 34H to represent “4”.
The ASCII codes for the digits 0 to 9 and the characters A to F are as follows:
Character ‘0’ ‘1’ ‘2’ ‘3’ ‘4’ ‘5’ ‘6’ ‘7’
ASCII code 30H 31H 32H 33H 34H 35H 36H 37H
Character ‘8’ ‘9’ ‘A’ ‘B’ ‘C’ ‘D’ ‘E’ ‘F’
ASCII code 38H 39H 41H 42H 43H 44H 45H 46H
RTU mode:
Every 8-bit data frame consists of two 4-bit characters (hexadecimal). For example, if “64H” is
transmitted between two stations using RTU, it is transmitted directly, which is more efficient than
ASCII mode.
Characters are encoded into the frames and transmitted in series. The method for checking each
type of frame is as follows.
10-bit character frame (for 7-bit character)
7N2
Start
bit
Stop
bit
Stop
bit
0 1 2 3 4 5 6
7-data bits
10-bit character frame
L H H
7E1
Start
bit
Even
Parity
Stop
bit
0 1 2 3 4 5 6
7-data bits
10-bit character frame
L H
7O1
Start
bit
Odd
Parity
Stop
bit
0 1 2 3 4 5 6
7-data bits
10-bit character frame
L H