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18.3 Connection to Modbus
Connection to RS-485
A screened, twisted-pair cable should be used. The cable screen must be connected to the COM terminal and
connected to safety ground at one point.
NOTE: In some cases, better performance is achieved if no COM connection is made. Device can operate with 2 wire connection.
Speed, parity and address
Modbus RTU
By default, each device is set to 19200-E-1 (even parity), address 245. Properly set registers in
section “0 VR control register” to congure each device before connecting it to existing network.
Optionally power each device one by one, conguring the settings before adding another one.
Termination
VR Series module contains neither termination nor bias circuitry.
RS-485 wiring should be externally terminated if needed.
For short wiring and/or low baud rate, interface can operate without termination. However, it is recommended
that termination (100-150 ohm resistor) is added on both ends of bus wiring. There are wiring length limits
regarding to speed and termination:
Maximum speed
[baud]
Maximum cable length ft. (m)
38400 4000 (1200), terminated cable
9600 4000 (1200)
19200 1600 (500)
38400 800 (250
NOTE: Any branch/derivative cable is considered unterminated. Keep them short, below 250m combined for maximum speed and reliability.
Ethernet bus
Ethernet related interface
Terminal Designation Terminal description
MODE Can be used to reset network conguration.
LED1 / LINK Slowly blinking when module is powered, permanently lid when link established.
Ethernet 10BASE-T RJ-45 connector.
LED2 / ACT Indicates Ethernet or RS-485 activity.
Services
• Http server on port 80
• Modbus server on port 502
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