Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!zaphod.mps.ohio-state.edu!wuarchive!udel!rochester!rit!ultb!clf3678
From: clf3678@ultb.isc.rit.edu (C.L. Freemesser)
Newsgroups: comp.sys.atari.st
Subject: Re: media change problem with Toshiba drive
Summary: It's a common problem
Message-ID: <1856@ultb.isc.rit.edu>
Date: 4 Jan 90 16:09:13 GMT
References: <7193@shlump.nac.dec.com>
Reply-To: clf3678@ultb.isc.rit.edu (C.L. Freemesser)
Organization: Information Systems and Computing @ RIT, Rochester, New York
Lines: 42

>	I read most of the messages on using generic drives with the ST and
>	didn't expect any problems but . . .
>
>	I'm adding a Toshiba ND-352TH-A also known as FDD4216G0D as a
>	second floppy.  If I leave the media change diode 
>	(pin 34 ---|<|--- pin 28) out, everything works fine, except of 
>	course media change is not detected.  With the diode, once the disk 
>	is removed once it always appears write protected.
>
 This is a common problem with home-brew drives.  There are a number of
solutions to this problem:

1) Get TOS 1.4.  It fixes the problem for good by forcing a re-read of
the disk every time it is accessed.

2) Run a jumper between pins 2 and 28 of your drive.  On some drives,
   this will solve the problem.  However, the ND-352 isn't one of these.
   The signal becomes too weak.  TO boost it, use a 74HC14 buffer chip.

3) Install a momentary on switch between pins 2 and 28.  When you insert
   a disk, hold the button down, and it will detect the media change,
   and not screw up write protect.  This is somewhat clunky, but it
   works.

>		1) What is the media change signal really supposed to do?
>	    	   I guess that really is, what does Atari expect it to do?
>		2) What is supposed to reset it from the "media change"
>		   condition?

The ST hooks these two lines together (pins 2 and 28).  As I said
before, just hook em together.

>		3) Is it possible to use this drive with the ST?

Yes, very possible.  


Chris Freemesser, Rochester Institute of Technology :BITNET:%clf3678@RITVAX
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