Chpater 6 MODBUS Communication
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6.3 MODBUS Communication Protocol
MODBUS communication protocol is only used when Pn700.2 is set to 1. There are two modes for
MODBUS communication: ASCII (American Standard Code for information interchange) mode and RTU
(Remote Terminal Unit) mode.
The next section describes the two communication modes.
6.3.1 Code Meaning
ASCII
ASCII
ASCII
ASCII Mode
Mode
Mode
Mode
：
Every 8-bit data is consisted by two ASCII characters. For example: One 1-byte data 64 H
（
Hexadecim al
expression
）
is expressed as ASCII code ‘64’, which contains ‘6’ as ASCII code 36
H
and ‘4’as ASCII code
34
H
.
ASCII code for number 0 to 9
、
character A to F are as follows:
RTU
RTU
RTU
RTU Mode
Mode
Mode
Mode
：
Every 8-bit data is consisted by two 4-bit hexadecimal data, that is to say, a normal hexadecimal data.
For example: decimal data 100 can be expressed as 64
H
by 1-byte RTU data.
Data Structure
：
10-bit
10-bit
10-bit
10-bit character
character
character
character form
form
form
form
（
7-bit
7-bit
7-bit
7-bit data
data
data
data
）
Character
‘0’
‘1’
‘2’
‘3’
‘4’
‘5’
‘6’
‘7’
ASCII Code
30
H
31
H
32
H
33
H
34
H
35
H
36
H
37
H
Character
‘8’
‘9’
‘A’
‘B’
‘C’
‘D’
‘E’
‘F’
ASCII Code
38
H
39
H
41
H
42
H
43
H
44
H
45
H
46
H
Start
b it
0
1
2
3
4
5
6
Stop
b it
Stop
b it
7-data bits
1 0 - bits character frame
P n 7 0 0 .1=0
：
7
，
N
，
2
（
M odbus
，
A SC II
）
Start
b it
0
1
2
3
4
5
6
Even
p a rity
Stop
b it
7-data bits
1 0 - bits character frame
P n 7 0 0 .1=1
：
7
，
E
，
1
（
M odbus
，
A SC II
）
