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RS-422 is used for long-distance point-to-point connections. RS-
422 originally used four wires for one-way communication (with
devices such as display terminals or printer) but was later adopted
by the industry for simultaneous two-way communication by
doubling the number of wires.
Each pin on the first device connects to a corresponding device
on the second. Flow control lines manage the communication.
The following table shows pin connections.
Pin
1
2
3
4
5
6
7
8
9
In a typical RS-485 application, the host device requests data
from a slave module then listens for the response. The host
transmits and receives data on the same pair of wires. Software
handles the flow control; no other wires are needed.
Pin assignments appear in the following table. Pins 1 and 4 share
the Data- wire. Pins 2 and 3 share the Data+ wire.
Pin
1
4
2
3
5
28 SBC-410 User's Manual
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Signal
TX-
TX+
RX+
<
RX-
<
Ground <
RTS-
RTS+
CTS+
<
CTS-
<
Signal
TX-
Data-
RX-
TX+
Data+
RX+
Ground
Pin
Signal
>
4
RX-
>
3
RX+
2
TX+
1
TX-
5
Ground
>
9
CTS-
>
8
CTS+
7
RTS+
6
RTS-
Pin
Signal
1
TX-
4
RX-
2
TX+
3
RX+
5
Ground
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