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5.3 Modbus
RTU MODBUS COMMUNICATION PROTOCOL
The system communication is performed serially in
RS-485 standard, with enclosed protocol. To convert
to Modbus RTU protocol, the K35402026 converter
should be used (called Gateway).
IMPORTANT
Features
1. “Modbus Gateway” is a slave device.
2. The RS485 standard is robust to noise and interference, but the higher the distance the shorter the transmission rate.
Maximum distance is 1200 meters. Distance to maintain maximum transmission rate is up to 12 meters.
3. Standard format Request Frame (TX):
Address
Function
Recorder Start
No. Recorders
CRC
1 byte
1 byte
2 bytes
2 bytes
2 bytes
4. The setting of the DIP existing in Gateway should be carried out as follows (as indicated by the dashed lines):
FIG. 23 - Modbus Kit
8
7
6
5
4
3
2
1
Description
Check
Transmiss
ion Rate
Address
0
0
No parity, 2 stop bit
0
1
Even, 1 stop bit
1
0
Odd, 1 stop bit
1
1
No check, 2 stop bit
0
0
19200
0
1
9600
1
0
4800
1
1
2400
0
0
0
0
Gateway Address 1
0
0
0
1
Gateway Address 2
0
0
1
0
Gateway Address 3
0
0
1
1
Gateway Address 4
0
1
0
0
Gateway Address 5
0
1
0
1
Gateway Address 6
0
1
1
0
Gateway Address 7
0
1
1
1
Gateway Address 8
1
0
0
0
Gateway Address 9
1
0
0
1
Gateway Address 10
...
...
...
...
... up until ...
1
1
1
1
Gateway Address 16
