[channelf] Re: Pacman Graphics Demo
- From: "Sean Riddle" <seanriddle@xxxxxxx>
- To: <channelf@xxxxxxxxxxxxx>
- Date: Sat, 30 Oct 2004 11:12:12 -0500
Thomas-
I disassembled the BIOS so I could patch it to location $800 to run
as a cart, but I just checked out the file and I didn't add any notes. =
One
thing I do to every cart I disassemble is to put a blank line after =
every
JMP, PK, POP, BF T0, and LR P0,Q statements. Those all change the =
program
flow, and separating them helps show the logical layout of the code. =
Every
line after a blank line should have a branch, jump, subroutine call or =
DCI
to it from somewhere.
I also look at every DCI and if it is valid, mark the corresponding
location as data. Likewise, I look at PI statements and try to figure =
out
what the subroutine is doing. Getting an idea of what the scratchpad
registers are used for is good.
Another tip is to look for IN and OUT statements, which will help
you figure out what a subroutine does.
If you haven't done it, you should compile MESS with debugging
support. That way you can stop any cart at any time and look at or =
change
the registers, set breakpoints, etc.
I've put on my web site
(http://members.cox.net/seanandalicia/chanfinfo.html) 2 disassemblies =
that I
made: cart 17 and cart 1. I worked on cart 17 a long time ago because =
it
didn't work with MESS. There was a CPU emulation error that I tracked =
down
by disassembling the code and figuring out what wasn't working =
correctly. I
disassembled cart 1 looking (in vain) for an Easter egg.
Sean
-----Original Message-----
From: channelf-bounce@xxxxxxxxxxxxx =
[mailto:channelf-bounce@xxxxxxxxxxxxx]
On Behalf Of Thomas Mathys
Sent: Saturday, October 30, 2004 9:20 AM
To: channelf@xxxxxxxxxxxxx
Subject: [channelf] Re: Pacman Graphics Demo
>games. I really like having an F8 DASM, by the way... shall I put this
>up for download somewhere,
no, don't, it's a preliminary version. work with it for now, but i =
improved=20
the whole thing a bit in the meantime and sent the final source to =
andrew,=20
who maintains dasm and will put up the offical version with f8 support.=20
code you write now will still assemble with the final version, as i =
didn't=20
change anything that would affect source code (i just improved the error =
handling. the version you have aborts assembly as soon as it finds an=20
error, while the final version will continue assembly, so that it can =
find=20
possible other errors in one go)
>or create a ves.h with all the BIOS calls
>in it for Channel F programmers to use? I can if it's needed...
that would be indeed a good thing. btw, is there a bios disassembly =
around ?
cheers
thomas
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