AWCTTYPA@UIAMVS.BITNET ("David A. Lyons") (04/11/89)
>Date: Fri, 7 Apr 89 19:01:49 GMT >From: Bevan Wang <marque!carroll1!acct015@CSD4.MILW.WISC.EDU> >Subject: Vectors... > >Does anyone know how the Reset vector works? And why the values differ >in ProD[OS] and DOS 3.3? Also what the heck is the USER Control-Y vector, >the Non-maskable interrupt vector? The system jumps through the reset vector ($3F2-3) after cleaning things up when Reset is pressed. If the power-up byte at $3F4 is not $3F3 EOR #$A5, then the system reboots instead. ProDOS doesn't fiddle with the RESET vector itself: its value depends on what SYS program you're using (BASIC.SYSTEM, for example). The Ctrl-Y vector at $3F8-A should be a JMP. It is called by the Ctrl-Y command in the monitor. The NMI vector at $3FB-D is called when an NMI occurs--it should be a JMP, too. No Apple machines make use of the NMI, but you can attach a wire and a pushbutton to it yourself if you really feel like it. (Don't attempt to return from an NMI, though, and be careful--you could mess up a disk by interrupting at the wrong time.) >Bevan R.S. Wang >acct015@carroll1.UUCP --David A. Lyons bitnet: awcttypa@uiamvs DAL Systems CompuServe: 72177,3233 P.O. Box 287 GEnie mail: D.LYONS2 North Liberty, IA 52317 AppleLinkPE: Dave Lyons (Watch this space! New U.S. mail address & net address will appear.)
c08_d103@jhunix.HCF.JHU.EDU (Ex-God) (04/13/89)
You can do a lot of interesting things with NMIs -- for example, most
of the copy cards and interrupt-and-print-the-screen cards work with
NMIs. Unfortunately, most of the interesting information about NMIs
comes from pirates (who have obvious interest in the subject), so it
doesn't tend to be discussed much on legitimate boards....
-- Andrew Barnert (Andy Social/Andy Christ/Andy Matter/ex-God)
ins_balb@jhunix/ins_balb@jhuvms/c08_d103@jhunix
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