Chapter 8 Communication Function
8-77
Example program 2
It’ s supposed that K7 base unit is the master and it reads Coil Status of the station no. 17, a Modicon product.
The master reads status of the input contact 10197 ~ 10218 of the slave station no. 17.
The input contact of the slave station is supposed to be as follows and the data that are read is saved in M015.
Input
10220
10219
10218
10217
10216
10215
10214
10213
10212
10211
10210
10209
Status
X
X
1
1
0
1
0
1
1
1
0
1
Hex
3
5
D
Input
10208
10207
10206
10205
10204
10203
10202
10201
10200
10199
10198
10197
Status
1
0
1
1
1
0
1
0
1
1
0
0
Hex
B
A
C
The status of input contact 10219,10220 are redundancy.
Data is sent starting from the low bit by byte unit. If the deficient bit of a byte is filled with 0. An example of sending the above data is
as follows.
Example 1) AC DB 35
Program
ᐭ
:
It designates slave station and function code
No. of station : h11(17) , function code : h02
ᐮ
: Address setting
Address ‘ 0’ at MODBUS protocol means address ‘ 1’ actually .So if you want to designate address ‘ 10197’ ,
write address ‘ 10196’
ᐯ
:
Reading number setting
Reading number is 22 from 10197 to 10220.
ᐰ
:
This is MODBUS Communication instruction.
The data transmission starts lower byte. The remnant part of byte is filled with ‘ 0’
Example 2) AC DB 35
Stored data at D200,D201
Device
Stored data
D200
h AC
DB
D201
h 00 35
ᐭ
ᐮ
ᐯ
ᐰ