HwB: Macintosh RS-422 Connector

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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 Цgren, Pierre Olivier, ">Ben Harris, Nathan Schmidt
Sources: comp.sys.mac.comm FAQ Part 1
Sources: Apple Tech Info Library, Article ID: TECHINFO-0001699
Please send any comments to Joakim Цgren.