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User Manual
Modbus Master / Ethernet
Document code: MN67506_ENG Revision 1.012 Page 12 of 18
ETHERNET PROTOCOL:
This protocol is able to read and write frames in the ModBus net. This protocol is very simple; you must known only the “Type of Data”, the
“Device Address” and the “Number of Point”. When the device responds the answere is transferred into the Ethernet.
W
RITE
F
RAMES
:
The transmission has a fixed structure that consist of seven bytes plus the data.
Byte Number
Description
1
Write Identifier (Write=0x02)
2
Type of Data
3
Device Address
4
Start Address Hi
5
Start Address Lo
6
Number of Point Hi
7
Number of Point Lo
8÷n+1
Data
n=”Number of Point *2” if Type of Data is 0x10 or n=”(Number of Point+7)/8” if Type of Data is 0x0F
The “Type of Data” (Byte Number 2) can have four values:
0x05: Write single Coil Status
0x06: Write single Holding Register
0x0F: Write multiple Coil Register
0x10: Write multiple Holding Register