2 Feb
2009
2 Feb
'09
7:13 a.m.
----------------------------------------
From: cclist at sydex.com
To: cctalk at classiccmp.org
Date: Sun, 1 Feb 2009 23:56:43 -0800
Subject: Re: speaking of 3.5" floppies, is 720K R.I.P.?
On 1 Feb 2009 at 10:11, Chris Elmquist wrote:
Hi
I'd given up on finding ones with the /READY signal.
I needed one to add double sided to my Canon Cat. It
had a Canon with a weird 20 pin cable that I just recently
figured out the wiring. I made a circuit with three ttl
chips to recreate the /READY that works well enough.
I had to make a cable translator anyway so I had
a piece of proto board to add the chips on.
I'd found a nice source of cheap 3.5 drives with
the 720K switch at Weirdstuff here in Sunnyvale.
They're mostly Teac FD235HF drives but I like the
Teac drives anyway. The price is right and all
the drives I've bought work fine( $5 ). They're
pulls but I don't let that bother me.
The circuit is simple enough that one could use
a registered PLA but one still needs the drive
current of a 7438. Maybe doubling or tripling
a few outputs would be enough as it is only the
one signal needed for the /READY. I also needed
to recreate the selects and motor signals from
a single select and motor enable.
Dwight
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What's particularly nasty is that I chose
these drives, Samsung SFD-321B,
because I had a recent datasheet that clearly showed they supported
this mode-- until of course they arrived and the switch/sensor is not
even installed!
Chris, the OEM manual for the SFD-321B is online at:
www.techtravels.org/amiga/SAMSUNG-SFD321B-070103.pdf
I note that they do use pin 2 as a density select pin and the OPA and
OPB PCB jumpers to determine the operating mode. You might want to
play with this a bit to see if you can coax it into operating in 2D
mode.
Whatever, please report back because I note that these drives are (1)
cheap and (2) have a provision to supply a READY signal instead of
DISK CHANGE. That could come in useful.
Cheers,
Chuck