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MMD > Archives > November 2014 > 2014.11.26 > 02Prev  Next


PianoDisc PDS-128Plus Floppy Drive Replacement
By Julie Porter

While the PianoDisc systems use standard floppy diskette drives,
they do not use the standard BIOS sectoring, so in order to read/write
PianoDisc floppies the BIOS has to be patched.  This is part of the
copy protection scheme where intentional errors are induced to the
diskette.  As I recall these have to do with the CRC checks, so you
will get bad track reads without the patch.

There is also no DOS directory or anything like that on a PianoDisc
floppy.  Many years ago, I posted a program here on the MMD called
"PDFile" which allowed access on a PC, with the appropriate BIOS
patches.  The music data on a PianoDisc floppy is a proprietary format
nothing like a Type 0 MIDI file.

Hardware-wise PianoDisc used the same floppy diskette drives as the
Commodore Amiga.  The Yamaha Disklavier, on the other hand, does use
standard DOS diskettes.  Yamaha writes invalid codes to the boot
sector which prevents DOS from reading the file names.

Around the same time I wrote "PDFile" I had a design for a stand-alone
controller that could play PianoDisc and Yamaha Disklavier diskettes as
well as Type 0 and Type 1 MIDI files.  This design used the same type
of chip that is now popular under the name Arduino.   Over the years
I modified the design to use Compact Flash Cards and then MicroSD
memory cards.  I have considered writing a floppy emulator but it is
much easier easy to just go straight to the SD card.

Floppy diskettes are inherently analog, so the emulator would have to
do a full D-to-A and then A-to-D conversion to match the correct phase
timings.  Most devices used a floppy controller chip (I still have a
tray of these).  This is what the BIOS talks to through a Register
file.  In this case the current track of the floppy shows up in a DMA
window.

Julie Porter

 [ Program "PDFile" for DOS is described by Julie at
 [ http://www.mmdigest.com/Archives/Digests/200411/2004.11.18.04.html 
 [ The program can be downloaded at
 [ http://www.mmdigest.com/Gallery/Tech/PDFILE.EXE  -- Robbie


(Message sent Thu 27 Nov 2014, 03:03:31 GMT, from time zone GMT-0800.)

Key Words in Subject:  Drive, Floppy, PDS-128Plus, PianoDisc, Replacement

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