Lantronix XPress-DR XPress-DR / XPress-DR-IAP - User Guide - Page 21

Screw-Terminal Serial Connectors, Table 2 - Serial Screw-Terminal Pinouts

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Introduction 1.6 Screw-Terminal Serial Connectors Table 2 - Serial Screw-Terminal Pinouts Pin Direction 1 To XPress DR 4 From XPress DR 2 To XPress DR 3 From XPress DR 8 Ground Name RXD or RXA TXD or TXA CTS or RXB RTS or TXB GND Function RS-232: RXD (Received Data) RS-422/485:RXA (Received Data -) RS-232: TXD (Transmit Data) RS-422/485: TXA (Transmit Data -) RS-232: CTS (Clear to Send) RS-422/485: RXB (Received Data +) RS-232: RTS (Request to Send) RS-422/485: TXB (Transmit Data +) Ground RXD CTS RTS TXD Rx- Rx+ Tx+ Tx- 1234 8 GND R Data+ Data- GND RxD- RxD+ TxD+ TxD- GND R R 12 34 12 34 8 R = 120 Ohm, 1/8 W RS-485 2-Wire 8 R = 120 Ohm, 1/8 W RS-422/485 4-Wire Note: For RS-485 2-wire functionality, pins 1 & 4 and 2 & 3 of the screw terminals must be connected together. Note: Termination resistors (R = 120 Ohm) are used to match impedance of a node to the impedance of the transmission (TX) line. Termination resistors should be placed only at the extreme ends of the data line, and no more than two terminations should be placed in any single segment of a RS-485 network. The terminator resistors may not be needed for your application. DSTni-XPress DR User Guide 1-7

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Introduction
1.6 Screw-Terminal Serial Connectors
Table 2 - Serial Screw-Terminal Pinouts
Pin
Direction
Name
Function
1
To XPress DR
RXD or RXA
RS-232: RXD (Received Data)
RS-422/485:RXA (Received Data -)
4
From XPress DR
TXD or TXA
RS-232: TXD (Transmit Data)
RS-422/485: TXA (Transmit Data -)
2
To XPress DR
CTS or RXB
RS-232: CTS (Clear to Send)
RS-422/485: RXB (Received Data +)
3
From XPress DR
RTS or TXB
RS-232: RTS (Request to Send)
RS-422/485: TXB (Transmit Data +)
8
Ground
GND
Ground
RXD CTS
RTS TXD
Rx-
Rx+
Tx+
Tx-
GND
1
2
3
4
8
Data+
Data- GND
1
2
3
4
8
R
R = 120 Ohm, 1/8 W
RxD-
1
2
3
4
8
R
R = 120 Ohm, 1/8 W
RS-485 2-Wire
RS-422/485 4-Wire
R
RxD+
TxD-
TxD+
GND
Note:
For RS-485 2-wire functionality, pins 1 & 4 and 2 & 3 of the screw terminals must be
connected together.
Note: Termination resistors (R = 120 Ohm) are used to match impedance of a node to the
impedance of the transmission (TX) line. Termination resistors should be placed only at the
extreme ends of the data line, and no more than two terminations should be placed in any
single segment of a RS-485 network. The terminator resistors may not be needed for your
application.
DSTni-XPress DR User Guide
1-7