Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!uakari.primate.wisc.edu!uflorida!mephisto!udel!freezer!gdtltr From: gdtltr@freezer.it.udel.edu (Gary Duzan) Newsgroups: comp.sys.atari.8bit Subject: Re: 6502 error conditions Message-ID: <30828@nigel.ee.udel.edu> Date: 18 Sep 90 14:27:41 GMT References: Sender: usenet@ee.udel.edu Reply-To: gdtltr@freezer.it.udel.edu (Gary Duzan) Distribution: comp Organization: Brain Dead Innovations (BDI) Lines: 24 Nntp-Posting-Host: mocha.it.udel.edu In article lennox@minilove.diag.stratus.com (Craig Scott Lennox) writes: => => =>What does the 6502 do when it encounters an illegal =>opcode? Does it just halt, as in a BRK, or can you have =>it branch to a trap address? => I believe the result is undefined. In fact, some early 6502's had some desirable side-effects of using an undocumented opcode, so programmers would use them. Obviously a bad thing. Newer chips like the 65802 and the 65816 actually use all 256 bit patterns for opcodes. (Well, just about anyway.) Answer: Don't do that. (0.5 :-) Gary Duzan Time Lord Third Regeneration -- gdtltr@freezer.it.udel.edu _o_ -------------------------- _o_ [|o o|] An isolated computer is a terribly lonely thing. [|o o|] |_O_| "Don't listen to me; I never do." -- Doctor Who |_O_|