ACME assembler and illegal/undocumented 6502 opcodes

ACME assembler and illegal/undocumented 6502 opcodes

Post by Kamelit » Mon, 20 Feb 2006 08:36:51


Hi,

I've a project that can't be assembled by ACME because it seems that thi
s assembler doesn't support illegal/undocumented 6502 opcodes.
While I can put them in hex in the source to bypass this limitation, I
first to know two things :

1) Do there's an official/unofficial version of ACME that support
illegal/undocumented 6502 opcodes ? (and where I can download it)

2) Do there's another assembler compatible with ACME syntax that support
illegal opcodes ?

I googled and think nothing interesting yet

Thanks for your help on that matter.

Regards,
Kamel
 
 
 

ACME assembler and illegal/undocumented 6502 opcodes

Post by uz » Mon, 20 Feb 2006 09:07:32


If ACME supports macros, it may be possible to implement illegal opcodes
using macros.

Regards


Uz


--
Ullrich von Bassewitz XXXX@XXXXX.COM
01:06:51 up 13 days, 9:59, 11 users, load average: 0.03, 0.15, 0.13

 
 
 

ACME assembler and illegal/undocumented 6502 opcodes

Post by John Selc » Tue, 21 Feb 2006 02:09:24


Why not simply put a .BYTE or .DB there?
 
 
 

ACME assembler and illegal/undocumented 6502 opcodes

Post by donn » Tue, 21 Feb 2006 02:35:52

WHY use illegal opcodes at all?
Using undocumented instructions is a crapy way to write progams.
 
 
 

ACME assembler and illegal/undocumented 6502 opcodes

Post by John Selc » Tue, 21 Feb 2006 03:01:26


They aren't undocumented:

http://www.yqcomputer.com/
 
 
 

ACME assembler and illegal/undocumented 6502 opcodes

Post by donn » Tue, 21 Feb 2006 03:51:34

They were undocumented by MOS.
And in later version of processors like the 65c02 and the 65c816 these
codes are used for other things.
So if you want to make your program incompatible with new hardware like
the C-1, go ahead use illegal opcodes.
 
 
 

ACME assembler and illegal/undocumented 6502 opcodes

Post by John Selc » Tue, 21 Feb 2006 03:58:24


So what? You can do a simple CPU test and use different routines.


The C-1 is not a C64.
 
 
 

ACME assembler and illegal/undocumented 6502 opcodes

Post by Peter van » Tue, 21 Feb 2006 04:06:49


To be more precise they were unintended side effects of the design of
the NMOS 6502 processor, which didn't attempt to trap illegal opcodes.
This is opposed to the Z80 which did have several opcodes designed in
that were not documented because these were not guaranteed to work
correctly on all Z80's due to chip fabrication issues.
 
 
 

ACME assembler and illegal/undocumented 6502 opcodes

Post by Kamelit » Tue, 21 Feb 2006 06:59:39


To be precise I'm trying to port a C64 game to another 6502 computer.
This game while being old (83) use such opcodes.

Regards,
Kamel

PS As for the C-1 I'd love to have one but its still beta and expansive
while having very few core.