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3. MODBUS GATEWAY SETUP & CONNECTIONS
NOTE: In this section, devices to be connected to the Modbus gateway's serial connection are simply
referred to as the "Modbus network".
CONNECTING THE POWER SUPPLY
Connect a DC power supply to the power terminals on the top of the Modbus gateway. Polarity
of the wires is indicated on the label on the side of the Modbus gateway. Acceptable voltages
are between 10 VDC and 48 VDC. The power supply must be capable of supplying 4 Watts for
MESR90x units or 6 Watts from MESR92x units.
CONNECTING MESR9xx MODBUS GATEWAYS TO MODBUS NETWORKS
MESR9xx Modbus Gateways can be configured to connect to Modbus networks using RS-232,
RS-422, RS-485 2-wire and RS-485 4-wire.
RS-232 connections support eight signal lines plus Signal Ground. Signals are single ended and
referenced to Ground. Default communications parameters are 9600, 8, N, 1 and no flow control
implemented.
RS-422 connections support two signal pairs: RXA(-), RXB(+) and TXA(-), TXB(+), plus GND.
The data lines are differential pairs (A & B) in which the B line is positive relative to the A line in
the idle (mark) state. Ground provides a common mode reference.
RS-485 connections support 2-wire or 4-wire operation.
When configured for 4-wire operation, the connection supports two signal pairs: RXA(-), RXB(+)
and TXA(-), TXB(+), plus GND. This makes full-duplex operation possible. The data lines are
differential pairs (A & B) in which the B line is positive relative to the A line in the idle (mark)
state. Ground provides a common mode reference.
When configured for 2-wire operation the connection supports one signal pair: DataB(+) and
DataA(-) signal channels using half-duplex operation. The data lines are differential with the Data
B line positive relative to Data A in the idle (mark) state. Ground provides a common mode
reference.
MESR9xx Modbus
MESR Power Connection
16
Gateways:
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