Apple II Emulation in HyperCard

["Jonathyn Bet'nct" <jonrelay@napanet.net>]

I'm writing my own Apple II emulator in HyperCard. I have most everything
working except peripheral cards, vertical blanking, analog game input, and
hi-res graphics. When I start it up, the emulated processor enters an
infinite loop:

$D4F0- D0 F8      BNE -8
$D4EA- B9 FB 01   LDA $01FB,Y
$D4ED- 88         DEY
$D4EE- 91 9B      STA ($9B),Y
$D4F0- D0 F8      BNE -8

I jumped to this address in ApplePC and it is a real infinite loop. I think
there's something wrong with how I initialize something or with the
processor emulation.

I have some other questions as well.

I have a clock cycle counter set up for accurate emulation. How many clock
cycles are there to a vertical blank? 525? 60? 16.666? How many for the
longest analog game input timeout?

What generates the other 7 bits when you access an I/O memory location where
only the most significant bit is used?

What are all the I/O memory locations for disk images, mouse cards, clock
cards, and so on and what _exactly_ does each do? (In English please; I
don't know C [yet :)].)




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