FM/MFM data separators (was: WD 1793 FDCs for sale) - test-drb@ccmp.vtda.org

23 Aug 2005

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Subject: FM/MFM data separators (was: WD 1793 FDCs for sale)
   From: Philip Pemberton <philpem at dsl.pipex.com>
   Date: Tue, 23 Aug 2005 08:16:24 +0100
     To: cctalk at classiccmp.org

In message <0ILN001WBHXEEOX0 at vms040.mailsrvcs.net>
          Allison <ajp166 at bellatlantic.net> wrote:

  If I can ever scan it there is a design I have
(NEC apnote) for a
 data seperator for FM/MFM that works for any rate and media.  Uses
 a prom and a latch (yes a state machine) to do synthetic PLL. Analog 
 PLLs were causing people too much pain and oneshots perform poorly. 
I would love a copy of that appnote - either scanned or photocopied is good
(if photocopied, I'll scan it and put it online myself). I've seen another
design that uses a state machine, but couldn't find any info on what it could
handle or how it worked. It's on
<http://www.simandl.cz/stranky/zxs/zxs_a.htm> if anyone's interested. 
That site has a copy of the circuit and the prom contents.  It can handle
all modes and rates.

...
 I'd really like to get my hands on any of the
Rockwell/MOS/Synertek
6502-series appnotes, or anything on the uPD765 or R6765. Also, has anyone
got any data on the Fairchild 96LS488? 
I'd like a scanner.

...
   Lacking that
if you can find SMC9229 or '39 part that does a lot 
 of the work for you. 
*checks Google
Obsolete and unobtainium. :(
The datasheet is probably on Bitsavers, but I doubt it's got any real info on
how the chip works internally. Certainly not enough to reimplement it from
off-the-shelf parts. 
It was never documeted on the fine detail.  As to unobtainium, I've managed
to find a few over time on XT and early at class FDC boards.  Likely there is
some NOS available somewhere.

Allison