Re: Apple IIe Memory Map

["Michael J. Mahon" <mjmahon@aol.com>]

simcop2387 wrote:
> After finding a copy listing of the memory map of the Apple IIe I've begun
> implementing it and all related hardware (I still don't have the core yet,
> that'll take another weekend probably)
>
> I've been looking at the source code to YAE and SDDApple and it would seem
> this is the memory map for $C000-$C07F (i'd like to know if i have this
> correct)

You really need to get a copy of the Apple II Reference Manual,
and probably a real Apple II to have any hope of really understanding
this stuff.

None of these memory-mapped I/O locations does any complex
function, like clear the area of memory representing the video
screen.  They only change the hardware modes or trigger hardware
operations, or read hardware values.

> $C000-$C00F	Keyboard Input
> $C010-$C01F	Keyboard Strobe/SoftSwitches? (i need to read more on this)

A reference to this address resets the high bit of the keyboard
input and "acknowledges" the keypress so that another can be
detected.

> $C020-$C02F	Tape Output?
> $C030-$C03F	Speaker Output (appears to be toggle based)
> $C040-$C04F	Unknown?

Each reference causes a 1 microsecond strobe output at a pin on
the "game port" on a real Apple ][.  Not useful for an emulator.

> $C050-$C057	Video Routines? (clear screen, and a few others?)

Sets video modes, but doesn't alter memory (clear screen).

> $C060-$C060	Tape IN?
> $C061-$C067	Buttons and Paddles
> $C070-$C07D	(bit confused on this one) but it appears to trigger the
> paddles

A reference to an address in the $C07X block triggers the paddle timers
to prepare for a paddle read.  For an emulator, this just warns you that
soon you will see a paddle timing loop executing, which expects to time
out in a time proportional to the selected paddle setting.

> $C07E-$C07F	would appear to be something to do with what YAE calls IOUDIS?
> and possibly HiRes?

The IOU is a //e-specific chip, with functions not available in the ][
or ][+.

> $C080-$C0FF	appear to be related to slot cards (address>>4 & 7 gives you
> the slot)

$C080 + slot number * 16 is the base address for a block of 16 addresses
that are decoded to control slot cards.  Their functions depend on the
architecture of the slot card.

> is anyone able to help clarify any of the places i seem to be misguided on
> or unclear?

As I said, you really need the manual, plus hands-on experience,
to make sense of all this with enough fidelity to write an emulator.

-michael

Music synthesis for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

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