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From: jb10320@uxa.cso.uiuc.edu (Desdinova)
Newsgroups: comp.sys.apple2
Subject: Re: Assembly Assistance
Message-ID: <1990Oct1.014717.4793@ux1.cso.uiuc.edu>
Date: 1 Oct 90 01:47:17 GMT
References: <12275@chaph.usc.edu>
Sender: news@ux1.cso.uiuc.edu (News)
Organization: University of Illinois at Urbana
Lines: 37

In article <12275@chaph.usc.edu> dickson@nunki.usc.edu (Jeffrey Dickson) writes:
>
>I need some quick help here, if you please...
>
>I require a fragment of 65816 code to do the equivalent of the Monitor's
>Control-N command, that is, put the CPU in native mode from the ProDOS 8/
>Applesoft environment.  I've tried playing around with the XCE, SEC, and SEP
>instructions, but I couldn't find a combination that would change the x,m, and
>e bits.  I know I'm missing something really simple here....
>
>Thanx........  Jeff
Gee! An actual "How do I do this" question, instead of a bitch question.
The code you're looking for looks like the following:

   clc
   xce		; put processor in native mode (allow 16-bit regs)
   rep #$30     ; actually invoke 16-bit registers

To go back to emulation mode, do the following:

   sep #$30
   sec
   xce

Note that you need to preserve such beasties as the data bank and
direct page registers.  Your 65816 assembly manual should have
something to say about that, I forget the exact instruction
names.

>dickson@chaph.usc.edu

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