Re: Apple ][ plus 13 sector! Problems...

["Bill Garber" <willy46pa@comcast DOT net>]

"Joseph Oswald" <josephoswaldgg@hotmail.com> wrote in message
e86bd0ec.0407201620.249727a2@posting.google.com">news:e86bd0ec.0407201620.249727a2@posting.google.com...
: pausch@saaf.se (Paul Schlyter) wrote in message
news:<cditc0$2mo0$1@merope.saaf.se>...
:
: > No, the controller doesn't detect anything by the MSB being
1.  The
: > controller merely transfers whatever bits it reads off the
disk into
: > its 8-bit shift register.  Then it's the responsibility of
the software
: > (i.e. RWTS) to read a valid nibble by reading the shift
register at the
: > appropriate time.
:
: Actually, the sequencer code *does* keep track of whether the
high bit
: of the data shift register is one; this is probably the
trickiest part
: of understanding the Woz state machine. In write mode, it has
to keep
: track, because that determines whether the "high numbered"
states with
: the write pulse = 1 or the "low numbered" state with the write
pulse =
: 0 get executed. _Beneath Apple DOS/ProDOS_ totally skimp on
their
: description of write mode, but if you look at the schematic,
you see
: the connection. In read mode, the state machine logic holds off
on
: shifting in the bits of the next byte when the data register is
: high-bit 1, by taking separate branches for "10" and "11"
:
: Just for my own records, <a
:
href="http://216.239.41.104/search?q=cache:eLu67H9GUXUJ:www.cs.um
u.se/~christer/Apple/p6.notes.html+christer+P6&hl=en">Here</a>
: is a link to a Google cache of a P6 rom description.

Don't know why, but I understand that better reading
it on my monitor screen than I did after reading it
in the book.  :o)

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - willy46pa @ comcast DOT net
Change DOT to a dot to contact me



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