Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!ucsd!ucsdhub!hp-sdd!hplabs!hpda!hpcuhb!hpcllla!hpclisp!hpclkms!ken
From: ken@hpclkms.HP.COM (Kenneth Sumrall)
Newsgroups: comp.sys.atari.8bit
Subject: Re: Need a cassette tape drive.
Message-ID: <1270006@hpclkms.HP.COM>
Date: 20 Oct 88 21:13:42 GMT
References: <736@wsccs.UUCP>
Organization: HP NSG/ISD California Language Lab
Lines: 47

/ hpclkms:comp.sys.atari.8bit / gdtltr@vax1.acs.udel.EDU (Gary D Duzan) /  7:49 pm  Oct 19, 1988 /
>>
>>3) I don't imagine the interface to a standard tape recorder should be too
>>   complicated; data is stored and retreived as audio tones on, I believe, 
>>   the LEFT channel of a standard stereo recording, with capability to play
>>   right-channel audio through the TV/monitor speaker!  You should be able  
>>   to simply connect the audio inputs, outputs, and ground, to the appropriate
>>   SIO pins, as well as using some kind of control circuit (I do NOT recommend
>>   direct connection here) to turn the cassette player's MOTOR on and off in
>>   response to the appropriate SIO signals.  (On the other hand, you could
>>   probably get away with leaving it ALWAYS on, in some if not all cases.  There
>>   ARE cases where the computer NEEDS to start and stop the tape, however.)
>>
>>   I think you will find it more complicated than you think. Remember that all
>I/O devices attached to the SIO port MUST BE INTELLIGENT!!! I believe the
>1050 drive has a microprocessor almost as powerful as the 6502 (not a great
>statement, but it is better than nothing). An SIO call sends data to the
>processor on the device and the device responds with the proper data, not just
>some sounds. There is a pin on the SIO to allow an audio signal to pass though
>the computer and out through your monitor speaker and a motor on/off pin, so
>you could probably get it to play, but reading data off it is out of the
>question without a processor chip.
>

You can make an interface to connect a standard tape recorder to the Atari.
However, you must first build a little circuit.  The reason is that the 
Atari uses FSK modulation of the signal when it stores it on the tape, and
you must add this FSK circuitry between the Atari and a standard tape
recorder.  Someone designed such a circuit and published it in the now defunct
magazine Popular Electronics.  I don't remember when it was published, but it
was at least three years ago.  If you can't find it, I will go through my
back issues and find the issue for you.

Also, even though the SIO bus is intelligent, and the 1050 disk drive has
a 6507 CPU, (which is a limited addressing, limited interrupts version of the
6502), the tape recorder is a dumb device.  It uses the motor start stop 
to control the tape deck, and has no feedback as to whether the data was 
written properly.  The ONLY time I ever use my tape recorder is when I get
old software on tape, and I want to move it to disk.  I then junk the
tape, and put the tape drive back in the closet.  (I used to play Pink Floyd
tapes through the TV speaker before I had a stereo in the same room as the
Atari, but that was 8+ years ago.)

Hope this helps.

Kenneth Sumrall
ken%hpclkms@hplabs.hp.com
...!hplabs!hpclkms!ken