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From: hcj@lzsc.ATT.COM (HC Johnson)
Newsgroups: comp.sys.atari.st
Subject: Re: floppy disk-change (again)
Summary: no disk change, uses media present
Message-ID: <1497@lzsc.ATT.COM>
Date: 26 Mar 90 16:44:48 GMT
References: <1990Mar24.192858.1655@ns.network.com>
Organization: AT&T BL Middletown/Lincroft NJ USA
Lines: 23

In article <1990Mar24.192858.1655@ns.network.com>, logajan@ns.network.com (John Logajan) writes:
> From time to time I've seen mention of replacement floppy drives not indicating
> disk change status.  Since I've had a replacement drive for longer than my
> human memory works, I don't recall if the original could really detect disk
> change status either.
> 
> Looking at the pinouts and schematics for a 520 ST reveals that there is
> no dedicated "disk change" signal.  So if the original Atari floppy drives

The problem is that ATARI uses the media present information.
If the media is removed, it is detected, and when it reappears, GOTCHA.

But, the same line also passes Write Protect info, so when a disk is write
protected, TOS can't tell if its removed (I think I got that straight).

Also, for those who notice there drive select light flickering dimmly:
TOS polls the drives at V Blank time to see if there has been a media
change.  This requires a very brief drive select.

Howard C. Johnson
ATT Bell Labs
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