Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!haven!umd5!hans
From: hans@umd5.umd.edu (Hans Breitenlohner)
Newsgroups: comp.sys.atari.8bit
Subject: Re: Need a cassette tape drive.
Message-ID: <4162@umd5.umd.edu>
Date: 21 Oct 88 23:51:12 GMT
References: <736@wsccs.UUCP> <4408@bsu-cs.UUCP>
Reply-To: hans@umd5.umd.edu (Hans Breitenlohner)
Organization: University of Maryland, College Park
Lines: 17

There have been some confusing ideas thrown about lately regarding
cassette interfaces, so I would like to clear some of this up.
(Of course, I don't know why anybody should believe my version over
anybody else's!)

Atari cassette recorders are dumb.  I have seen the inside of one myself,
and there is almost nothing in them.  Also I understand that the 1010
is no better than the 810, just repackaged.

Data is recorded serially (obviously), I believe at 600 baud.  For recording
the computer generates the tones (for two tone, of FSK recording mode), and
the cassette drive simply records the audio signal.  For playback the 
cassette drive converts the tone to a logic level, which is fed back to the
computer.  The circuit is primitive, nothing so fancy as a PLL.  But you do
need stuff beyond what a tape recorder will give you.

The early issues of Antic had a column just on stuff such as this.  I would
encourage to try to find some, they make interesting reading.