[A86] Re: Trying to keep the list (sort of) alive...
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[A86] Re: Trying to keep the list (sort of) alive...
On Sat, 7 Dec 2002 21:18:42 -0600 "Travis Evans" <travisevans@cox.net>
writes:
> Does anyone know why? Is this information wrong, or
> does VTI not emulate it correctly, or do certain
> conditions need to be met? Does anyone know how VTI
> resets the calculator when you use the "Reset
> Calculator" option from the right-click menu?
If you look through the startup code there it's kinda weird. It jumps to
$0e2e (on rom 1.2), where it does a slow sweep of the stack pointer
across video memory, which is probably what causes it to crash (try
disabling interrupts first?), then it enables interrupts and waits for
the interrupt routine to take over. I don't think the interrupt is ever
meant to return at this point because the code after that makes no sense.
(it prints something uninitialized to the screen and returns to
someplace it has no return address for)
The z80 will begin execution at $0000 whenever it restarts. I believe
there are two circumstances where this will happen under normal
operation: when you first start it, and when you turn it on after
replacing batteries. After replacing batteries, it doesn't reset RAM, so
there must be some sort of check for that. (I think it's the check if
port $06 is zero)
If rst $00 doesn't work even with di, I'd guess that VTI uses _initialize
at $4109. But I dunno, you could put a breakpoint at 0 and see what
happens when you reset it.
-josh
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