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From: ekijak@ARDC.ARPA (Edmund S. Kijak, POINT)
Newsgroups: net.micro.atari
Subject: Re: 800xl info request
Message-ID: <8510031251.AA12094@UCB-VAX.ARPA>
Date: Thu, 3-Oct-85 08:48:14 EDT
Article-I.D.: UCB-VAX.8510031251.AA12094
Posted: Thu Oct  3 08:48:14 1985
Date-Received: Fri, 4-Oct-85 06:18:55 EDT
Sender: daemon@ucbvax.ARPA
Organization: The ARPA Internet
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The four joystick ports are connected to two 6520 PIA (Peripheral Interface
Adaptor) chips.  Each bit of these ports can be set independently by software
to be either an output or an input, then can be written to or read from.
Specs for the 6520 can be gotten from Rockwell or Synertek.  Each joystick
port also contain pins for a pair of paddles.  These are variable resistors.
You can connect variable resistance sensors here and read them by software.
	Details are in the Atari Hardware Manual, or check old issues of
Byte and other mags (around 1982, 1983).