Chapter 8 Communication Function
8-76
Example program 1
It’ s supposed that MK80S base unit is the master and it reads Coil Status of the station no. 17, a Modicon product.
The master reads status of the Coil 00020 ~ 00056 of the slave station no. 17. The Coil of the slave station is supposed to be as follows
and the data that are read is saved in D1000
Coil
59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40
Status X X X11011000011101011
Hex1B0EB
Coil
39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20
Status 00100110101111001101
Hex 2 6 B C D
<Data status of the Modicon product’ s Coil 00020-00059>
The status of Coil 57, 58, 59 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) CD B2 0E 1B
Program
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It designates slave station and function code
No. of station : h11(17) , function code : h01
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: Address setting
Address ‘ 0’ at MODBUS protocol means address ‘ 1’ actually .So if you want to designate address ‘ 20’ , write address ‘ 19’
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Reading number setting
Reading number is 37 from 20 to 56.
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:
This is MODBUS Communication instruction.
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.
The data transmission starts lower byte. The remnant part of byte is filled with ‘ 0’
Example 1) CD B2 0E 1B
Stored data at D1000,D1001,D1002
Device Stored data
D1000 h CD 6B
D1001 h B2 CE
D1002 h 00 1B
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