Re: [stella] DASM wish list

Subject: Re: [stella] DASM wish list
From: "B. Watson" <atari@xxxxxxxxxxxxxx>
Date: Tue, 16 Aug 2005 15:38:20 -0400
On Tue, 16 Aug 2005, xucaen wrote:

> Hi, I just had a thought: A new assembler should be compatible with the
> books that have aleady been written on 6502 assembler.

A good idea.

However (there's always a however)...

So far as I know, there are no 6502 assembler books that have any
information on the illegal opcodes. There are at least two different
sets of names for the illegal opcodes...

Also, different books are written for use with different assemblers. Some
of them call "ROR A" just plain "ROR", and some don't... different
macro assemblers use different syntax for defining and calling macros.
Some assemblers, you set the current origin by assigning to "*", some
you use an "ORG" directive, and some allow both. Some assemblers use <
and > to mean low-byte and high-byte, and some don't support this (so you
have to use value/256 and value%256, except sometimes it's \ instead of %
to mean "modulus", and sometimes there's no modulus operator so you have
to use value>>8, except when there's no >> bit shift operator)...

The list goes on. There never was anything like an ANSI or ISO 6502
assembly standard. The chip documentation (as far as I know) specifies
the opcodes and addressing modes, but doesn't say anything about how an
assembler should handle symbols, expressions, directives, macros, etc.

I think it'd be literally impossible to support every 6502 assembly
dialect in the same assembler, even if it were desirable... The ATASM
project attempts to mimic the MAC/65 assembler, which is probably the
closest thing to a "standard" syntax in the Atari world, but it's a
limited syntax compared to DASM.

Sorry, I didn't mean to go into rant-mode on you. This is just one of
those irritating things that sets me off. Today seems to be my day for
ranting about problems without providing any useful solutions :(

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