3. Setup and Connections
Vlinx MESR9xx Modbus Gateway
Page 13
Manual Documentation Number MESR9xx-4508m
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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(-), TXA(+),
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(-), TXA(+), 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.
Connecting the MESR9x1-x
The
MESR9x1-x
has one serial connection that supports RS-232, RS-422 and RS-485
(2- and 4-wire). The unit has two connectors: a DB-9M connector and a 5-position
terminal block.
If you select RS-232 mode when you configure the Modbus gateway, you must connect
the Modbus network to the Modbus gateway via a serial cable. The MESR901 is a DTE.
If the Modbus network is a DTE, use a null modem (cross-over) cable. If the Modbus
network is a DCE, use a straight-through cable.
If you select RS-422 mode, RS-485 2-wire mode, or RS-485 4-wire mode when you
configure the Modbus gateway, you must connect the Modbus network appropriately, via
the 5-position terminal block.
Note: Refer to Appendix D for connector pinout information.
