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Macintosh RS-422

It's possible to connect RS-232 peripheral to the RS-422 port available on Macintosh computers. Use RXD- as RXD, TXD- as TXD, Ground RXD+, Leave TXD+ unconnected, GPi as CD.

8 PIN MINI-DIN FEMALE (at the computer)

8 PIN MINI-DIN FEMALE at the computer.

Pin Name Dir Description
1 HSKo --> Output Handshake
2 HSKi/CLK <-- Input Handshake or External Clock
3 TXD- --> Transmit Data (-)
4 GND --- Ground
5 RXD- <-- Receive Data (-)
6 TXD+ --> Transmit Data (+)
7 GPi <-- General Purpose Input
8 RXD+ <-- Receive Data (+)

Note: Direction is DTE (Computer) relative DCE (Modem).

Note: GPi is connected to SCC Data Carrier Detect (or to Receive/Transmit Clock if the VIA1 SYNC signal is high). Not connected on the Macintosh Plus, Classic, Classic II, LC, LC II or IIsi.

Contributor: Joakim Ögren, Pierre Olivier, Ben Harris, Nathan Schmidt

comp.sys.mac.comm FAQ Part 1, Apple Tech Info Library, Article ID: TECHINFO-0001699

Copyright © The Hardware Book Team 1996-2001.
May be copied and redistributed, partially or in whole, as appropriate.
Document last modified: 2001-06-08