Re: PET memory maps

From: Marko Mäkelä (
Date: 2002-01-18 11:56:40

On Thu, 17 Jan 2002, Ethan Dicks wrote:

> If VICE can give me a watchpoint that will trigger if a zero-page location
> is written to from a PC address above, say, $8000, then that's _exactly_
> what I need.

I don't know if it's possible to specify such a condition on the program
counter.  If it isn't, I'd just create a modified version of VICE.  I did
a similar thing with Pfau Zeh for cracking some ROM-protected VIC-20
cartridges.  Back then (1996 or 1997) I don't think that there was a
VIC-20 emulator in VICE, and the author of Pfau Zeh was kind enough to
give me the source code (or maybe it was publicly available, I don't

> > BTW, I just released cbmlink 0.9.1 and c2n 1.0.2, as both source code and
> > as 32-bit Windows executables, which have been tested on versions 98 and
> > 2000.  The next version will probably support 6551 based serial
> > connections on the CBM-II series and plus/4, and perhaps also on the
> > C64/C128 equipped with a cartridge.
> Cool.  I can't wait to buy/build one.  Might even want two!

The schematic diagrams and the board layouts have been there for several
weeks now.  But you'll probably want to wait until professionally made
circuit boards are available.  Rainer, could you report on that situation?

I've built two SMD prototypes so far.  The pictures of the first one are
on <URL:>.
I had to make some kludges to install the 8 MHz MA505 crystal in the place
of an SM49 case (or something) and the SO16 MAX232 in the place of an
SO16L slot.

The second one I built last weekend.  The vias were not through-coppered,
so I had to install jumper wires.  I did it in a hurry, and used something
like 4 to 6 hours to debug the beast (4 broken vias or almost unnoticeable
short-circuits near the vias).  Nevertheless, it works, the parts fit
perfectly.  My friend will use his connections (friend of a friend) to
have the rest of the prototype boards through-coppered.  But there will
only be something like 20-30 of these boards.

> > If you bypass the ROM routines, the same binary could run on all ROM
> > versions. 
> True.

But I forgot that there are no SETLFS or SETNAM routines in the PET ROM.
You'd need to know some ROM-dependent zero page locations in any case.

BTW, cbmlink's file operations are a bit buggy on the PET.  If no drive is
connected, the computer reports ?DEVICE NOT PRESENT on the screen and
aborts; a BASIC error message for a machine language program.


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