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From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.electronics
Subject: Re: Convert Music CD Player to Computer CD Reader
Summary: Not generally possible.  Not easy in any case.
Keywords: CD, project
Message-ID: <8319@milton.u.washington.edu>
Date: 29 Sep 90 20:31:39 GMT
References: <1043@digi.lonestar.org>
Organization: University of Washington, Seattle
Lines: 28

In article <1043@digi.lonestar.org> crichmon@digi.lonestar.org (Charles Richmond) writes:
>I would like to know what it would take to add some circuitry to
>an audio CD player so that a computer could read a CD rom on it.
>
>Any references on understanding the guts of an audio CD player would
>certainly help.

	Almost all audio CD players have a custom LSI chip that handles
the track detection/subcode decoding/complex interleave functions.  This
may (if you're lucky) be a general purpose microprocessor with a plug-in
EPROM.  Then you can read the EPROM, disassemble it, and change the
behavior.
	Otherwise, that LSI chip will be carefully identifying the
non-music tracks and skipping them.  There is no way to make a CD
player, intended for audio, read the non-audio tracks on a CD-ROM.
Some machines do both (I think the Apple CD-ROM reader is one such).
	Alas, I have perused several references on CD players and there's
no joy there.  The theory presented is sketchy, the mechanical details
are dismissed with handwaving, and the electronics is treated as
a black box to be replaced if it gives trouble.
	I have schematics for one player, and it's obvious that nothing
much can be done to change its behavior; the MSM6404RS chip that controls
the various machine operations might be possible to replace/reprogram,
but it has dedicated on-chip program ROM; I know of no way to read out the
existing program for analysis (and lotsa luck getting that info
from the manufacturer).

		John Whitmore