Reverse-engineering Snap (Panasonic HHC)

I've confirmed my earlier guess that Snap uses bytecode
rather than
pointers as a normal FORTH.  The BRK instruction ($00) is
used
for entry into Snap, and is followed by bytecodes.  The
interrupt
handler checks the B flag to see if a BRK occurred.  If so,
it pulls
the PC from the stack into registers, subtracts one, and
stores it into
the Snap instruction pointer at $0015/16.

The BRK handler and Snap primitives end with a jump to NEXT
at $0009, which
points to $CC2E. The code there fetches the byte pointed to
by the Snap
instruction pointer, and depending on the two high order
bits, jumps indirect
via jump tables from $c000-$c0ff, $c100-$c17f, or
$0000-$007f.

At least, that's what happens if the contents of $66 is
zero.  If it's
non-zero, it goes somewhere else, and I haven't figured out
what's up
with that.

Anyone else ever dig into the innards of Snap?

Eric

Just a reminder that the largest all encompassing event of
its kind is
this weekend in Wisconsin.

The Midwest Gaming Classic is dedicated to consoles,
computers, video
coin-ops and pinball from past to present.  There's a large
ammount of
displays, vendors, competitions, and the museum area (where
everything is
set up to use and enjoy, i.e. its all playable).  20,000
square feet, over
2 days.

Retro-computing wise, The Emergency Chicagoland Commodore
Convention group
will be having a Commodore area there, and there is also a
Tandy group
coming.  There will also be computing displays for Atari,
TI, Apple and
more....

They'll also be speakers -

Yours truly on the relaunch of Microprose
Walter Day of TwinGalaxies
Ben Heckendorn on console hacking
and more....

Olympia Resort and Conference Center
1350 Royale Mile Road
Oconomowoc, WI 53066
1-800-558-9573


    * Saturday, March 29, 2008 - 10:00am to 8:00pm
    * Sunday, March 30, 2008 - 10:00am to 5:00pm


If you're interested on showing off anything of yours the
last minute, let
me know and I can arrange for space.

This is not a "kiddies" gaming event, average age
is 30-45, so anything
you bring will be appreciated and enjoyed by the attendees.



www.midwestgamingclassic.com for more info, or email me
directly.




Marty

Hello Eric (and other HHC users),

all this talk has made me dig out my Panasonic HHC - I also
have the
printer (RL-P1004A).  Unfortunately I have no documentation
and no
ROMs that allow any sort of programming AFAICT...

I have 6 ROMS, 4 dated 10/02/86, and two 08/18/87.  They
appear to be
from La Laurentienne bank with some sort of banking software
with a
(c) QuadROM.  I don't think they would be of any particular
interest
to anyone (unless you need to recalculate your 1986 RRSP
contributions
for your Quebec provincial tax) but if anyone wants them to
examine/archive I'd be happy to send them.

Does the order of ROMs in the sockets matter? I would assume
so - but
there is no (obvious to me) indication of which ROM would go
where.

How difficult would it be to copy a ROM?  The bank ROMs are
simply
EPROMs with sticky paper labels, I think I could simply
erase one and
the reprogram it with a homebuild adapter so as not to
damage the
carrier...

Is there any information out there on how to program the HHC
in 6502
assembly?  memory maps, keyboard and LCD interface, etc...

Joe.

On Thu, 2008-03-27 at 23:32 -0400, Joachim Thiemann wrote:

> How difficult would it be to copy a ROM?  The bank ROMs
are simply
> EPROMs with sticky paper labels, I think I could simply
erase one and
> the reprogram it with a homebuild adapter so as not to
damage the
> carrier...

If it's just an ordinary ROM, extremely easy.  You just read
it, and
blow another.

I've taken to using Flash memory from scrapped motherboards,
with a
suitable adaptor to make it fit 28-pin sockets and the
additional
address lines held low.  It takes seconds to erase, rather
than half an
hour.

Gordon

Joachim Thiemann wrote:
> How difficult would it be to copy a ROM?  The bank ROMs
are simply
> EPROMs with sticky paper labels, I think I could simply
erase one and
> the reprogram it with a homebuild adapter so as not to
damage the
> carrier...

The EPROMs are most likely Motorola MCM68764, or (slightly
less desirable)
MCM68766.  It should be no problem to erase and reprogram
them.

The only interesting (IMHO) ROMs you can program into an
MC68764
(limited to 8K bytes) are the Microsoft BASIC ROM and the
Scientific
Calculator ROM.  SnapBASIC and SnapFORTH require 16KB, and
there are
no 16KB EPROMs that will fit the 24-pin carrier.

> Is there any information out there on how to program
the HHC in 6502
> assembly?  memory maps, keyboard and LCD interface,
etc...

I've been starting to reverse-engineer it, but it's a lot of
work.
Someone that did some HHC reverse-engineering back in
1981-1982 (due
to inadequate documentation from Friends Amis) is sending me
his
notes, and I should have them in a few days.  However, he
advises me
that since they were just notes to himself, they are
probably too
cryptic to be very useful.  Still, I'm hoping I can tease
some
information out of them.

Eric