MAMEWorld Forums - EmuChat - Re: MAME0148 Debugger & Cheats Question

> > > Debugger Window Frame #3: Top-right frame right of Instruction calls area
> >
> > They represent the "Instruction calls" (aka opcode and operand) as bytes, a Z80 16
> > bit jump opcode is represented by C3 and with an operand of $BEEF we have JP $BEEF
> > which we be represented by C3 EF BE (lo/hi byte order on the operand).
> >
> > > [Cheats Question]
> > > I would have posted these on Pugsy's forum but new accounts cannot be created
> right
> > > now:
> >
> > It's back on for a few days at least (spambot registrations...)
> >
> >
> > > Question 1: how does "FFDAE840" relate to "00B5D08"? I can set a breakpoint at
> > > "FFDAE840" and the debugger stops and the cheat works. However, I don't
> understand
> > > how instruction "FFDAE840" relates to "00B5D08". Is "00B5D08" a rom address
> (since
> > > this is a ROM cheat)?
> >
> > The simple formula for this is:
> > FF800000 + ( 00B5D08 * 8 ) = FFDAE840
> > That works for all ROM addresses
>
> Note that this formula only applies to Midway hardware using the TMS34010 CPU. The
> relation between ROM addresses and CPU addresses is different between CPU types and
> hardware, and the TMS34010 is particularly weird as it addresses individual bits
> rather than bytes--that's where the "times 8" comes from.
>
> Look at the ADDRESS_MAP macro in the source code for the MAME driver of the game
> you're debugging to see where ROM, RAM and input ports are.
>
> If you're completely new to debugging using MAME, I strongly advise that you start
> with a game that uses a Z80 or 68000 as the main CPU (and preferably one without
> encryption or bankswitching, so not CPS2 or NeoGeo. CPS1 is OK.) Machine code for
> these CPUs is relatively easy to read and there is a ton of documentation since both
> CPUs were used in popular home computers.

Thanks AWJ.

I did see somewhere (MAME cheats forum I think) that Midway machines had a tendency to be a pain in the ass. For some reason I always tend to find my way to the hard road

. Always good learning experiences, though.