Path: utzoo!attcan!uunet!snorkelwacker!apple!portal!cup.portal.com!Ordania-DM
From: Ordania-DM@cup.portal.com (Charles K Hughes)
Newsgroups: comp.sys.atari.8bit
Subject: Re: 6502 error conditions
Message-ID: <34057@cup.portal.com>
Date: 19 Sep 90 06:24:52 GMT
References: <LENNOX.90Sep18094730@minilove.diag.stratus.com><30828@nigel.ee
 .udel.edu> <LENNOX.90Sep18104900@minilove.diag.stratus.com>
Organization: The Portal System (TM)
Lines: 31

Craig Lennox writes:
>Well that's depressing.  I was hoping there would be an illegal opcode
>trap to implement new opcodes.

  To simulate this, use the BRK opcode.

>
>Guess I won't even ask if there's an illegal memory ref trap address
>to use to implement virtual memory.  (0.125 :-) )

  To simulate this, wire up a circuit that generates an interrupt if virtual
memory is accessed.


  Of course, the solution is to simply use a 68000.  It has everything you are
looking for I think.

>
>The really depressing thing is:  How tough could it have been?  I
>realise that the 6502 microcode really packs 'em in, but it's
>pretty poor programming style not to handle error conditions.

  Yes, but at the time the 6502 was created it wasn't really easy programming
them. :)

>
>
>--
>|    flame me at: lennox@minilove.diag.stratus.com, (Craig Scott Lennox)    |

Charles_K_Hughes@cup.portal.com