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c953616a71
There is one failing test, which I expect to fail at this point; that's because we need to write a read/write map function for the stack and zero page so that they use aux memory when BANK_ALTZP is on, and main memory when not.
270 lines
8.0 KiB
C
270 lines
8.0 KiB
C
#ifndef _APPLE2_H_
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#define _APPLE2_H_
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#include "apple2.dd.h"
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#include "mos6502.h"
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#include "vm_bitfont.h"
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#include "vm_screen.h"
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/*
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* This is the size of the bitmap font we use for the apple2
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*/
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#define APPLE2_SYSFONT_SIZE 21558
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/*
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* The reset vector is the address where the apple will consult to
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* figure out where control should go after a reset. Think of this as
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* something like a pointer to a main() function in C. That is: where's
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* the main function? Let's ask the reset vector!
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*/
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#define APPLE2_RESET_VECTOR 0x03F2
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/*
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* This is the address of the validity-check byte, aka the power-up
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* byte. The Apple II will use this to see if the reset vector is valid.
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*/
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#define APPLE2_POWERUP_BYTE 0x03F4
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/*
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* I'm not _exactly_ clear on where the applesoft interpreter lives in
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* ROM, after spending possibly too-much time researching how this
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* works. My guess is I'm missing something that's obvious to others.
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* $E000 seems to be the original spot that Integer BASIC was contained,
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* and I'm going to guess Applesoft BASIC is in the same spot. Here's
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* hoping!
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*/
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#define APPLE2_APPLESOFT_MAIN 0xE000
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enum video_modes {
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VIDEO_40COL_TEXT,
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VIDEO_LORES,
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VIDEO_HIRES,
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VIDEO_80COL_TEXT,
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VIDEO_DOUBLE_LORES,
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VIDEO_DOUBLE_HIRES,
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};
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enum color_modes {
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COLOR_GREEN,
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COLOR_AMBER,
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COLOR_GRAY,
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COLOR_FULL,
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};
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enum lores_colors {
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LORES_BLACK,
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LORES_MAGENTA,
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LORES_DARKBLUE,
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LORES_PURPLE,
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LORES_DARKGREEN,
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LORES_GRAY1,
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LORES_MEDBLUE,
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LORES_LIGHTBLUE,
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LORES_BROWN,
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LORES_ORANGE,
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LORES_GRAY2,
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LORES_PINK,
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LORES_LIGHTGREEN,
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LORES_YELLOW,
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LORES_AQUAMARINE,
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LORES_WHITE,
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};
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// Write-protect on/off.
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// Read target = ROM or RAM.
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// Write target = RAM.
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// Set mode of $Dxxx hexapage bank1 or bank2 ram.
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// 0 - 0=off 1=on
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// 1 - 0=ROM 1=RAM
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// 2 - 0=BANK1 1=BANK2
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/*
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* An Apple II has bank-switched memory beginning with $D000 extending
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* through $FFFF. The enums below define bit flag names to determine
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* what is accessible through those addresses.
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*
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* Note that it _is_ possible to write while reading ROM, but your
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* writes will not go to ROM; they'll go to _RAM_. Any write to $E000 -
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* $FFFF may only be sent to bank 1 RAM. Writes to $D000-$DFFF may
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* either be sent to bank 1 RAM or bank 2 RAM based upon the RAM2 bit
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* flag below.
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*/
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enum memory_mode {
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/*
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* By default, memory accesses go to main memory in _all_ cases.
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* Auxiliary memory is not used in any capacity.
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*/
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MEMORY_DEFAULT = 0x0,
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/*
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* When this is on, the core 48k (non bank-switchable) of memory
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* will be read from auxiliary memory. When off, it will be read
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* from main memory.
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*/
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MEMORY_READ_AUX = 0x1,
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/*
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* When on, writes to the core 48k of memory will go to aux; when
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* off, they go to main.
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*/
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MEMORY_WRITE_AUX = 0x2,
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/*
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* This bit is what the tech reference calls an "enabling" switch,
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* for PAGE2 and HIRES below. If this bit is not on, then those two
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* other bits don't do anything, and all aux memory access is
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* governed by WRITE_AUX and READ_AUX above.
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*/
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MEMORY_80STORE = 0x4,
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/*
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* When 80STORE is on, PAGE2 will allow you to access auxiliary
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* memory for the display page. The range depends on HIRES below.
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* When PAGE2 is on and HIRES is off, then PAGE2 causes accesses to
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* $0400..$07FF to always go to auxiliary memory (read or writes).
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* When both PAGE2 and HIRES are on, then $2000..$3FFF also go to
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* aux memory. When 80STORE is off, then these two bits are ignored.
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*/
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MEMORY_PAGE2 = 0x8,
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MEMORY_HIRES = 0x10,
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};
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enum bank_switch {
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/*
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* In nominal bank-switch mode, reads in the bank-switchable address
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* space go to ROM; writes to RAM are protected; and bank2 memory is
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* used.
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*/
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BANK_DEFAULT = 0x0,
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/*
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* When on, this reads from RAM in bank-switched memory. When off,
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* it reads from ROM.
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*/
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BANK_RAM = 0x1,
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/*
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* When on, we will write to RAM. When off, we will write-protect
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* RAM in bank-switched memory. NOTE: we can never write to ROM--or
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* else it wouldn't be ROM! So if you have BANK_RAM off, but
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* BANK_WRITE on, then writes do not fail, but they do go to RAM.
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*/
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BANK_WRITE = 0x2,
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/*
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* When this is on, we will use bank 2 RAM when accessing the $Dnnn
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* range; otherwise, we use bank 1 (as you might guess).
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*/
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BANK_RAM2 = 0x4,
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/*
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* This is a weird little bit. When BANK_ALTZP is on, the zero page
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* and stack are accessed from auxiliary memory rather than main
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* memory. Those two pages of memory, however, are _copied_ from one
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* to the other, so data should remain consistent.
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*
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* That's not the weird part. That part makes sense given the name
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* (which isn't my name, but is the name used in the IIe technical
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* reference). The part that isn't so obvious is that
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* bank-switchable RAM will _also_ be accessed from auxiliary
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* memory, not main memory. Note that aux memory has its own second
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* bank of RAM, the way that main memory does, so BANK_RAM2 works
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* the way you think, but it works with the aux RAM2. No data is
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* copied between main and aux's bank-switched memory, unlike the
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* way zero page and the stack are handled.
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*/
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BANK_ALTZP = 0x8,
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};
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typedef struct {
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/*
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* The apple 2 hardware used an MOS-6502 processor.
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*/
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mos6502 *cpu;
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/*
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* This is the main memory bank of the computer. Conventionally, it
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* contains not only the first contiguous 48k of RAM, but it also
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* contains the last 12k of bank 1 RAM.
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*/
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vm_segment *main;
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/*
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* The Apple II used a system of bank-switched memory to enable
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* software to address a separate block of ROM.
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*/
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vm_segment *rom;
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/*
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* The Apple II may have an auxiliary RAM bank; this was possible by
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* installing a card there. If you had the 80-column text card (and
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* you likely did), then you got an extra kilobyte of RAM to work
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* with; it was either used for the extra columns or you could take
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* advantage of it for extra storage otherwise.
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*/
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vm_segment *aux;
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/*
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* The screen wherein we shall render all of our graphics.
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*/
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vm_screen *screen;
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/*
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* This is the system font (the only font the Apple II knows about,
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* really); anywhere we render text, we have to use this font.
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*/
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vm_bitfont *sysfont;
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/*
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* This is the mode in which we must interpret graphics. This will
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* tell us not only if we're in lo- or hi-res, but also if we are in
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* single or double view mode.
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*/
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int video_mode;
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/*
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* This is the color mode we want to emulate. You can have a few
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* different styles of monochromatic displays: green, amber, and
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* light gray on black; you can also emulate a full color display,
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* in which text mode tends to look like light gray.
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*/
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int color_mode;
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/*
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* This describes the behavior of our bank-switching scheme. We need
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* our read/write mappers to know where writes into the
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* bank-switched area of memory should target.
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*/
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vm_8bit bank_switch;
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/*
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* Beside bank-switching, we also need to keep track of memory
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* modes; these pertain mostly to reading from main or auxiliary
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* memory.
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*/
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vm_8bit memory_mode;
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/*
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* Our two disk drives.
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*/
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apple2dd *drive1;
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apple2dd *drive2;
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} apple2;
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extern apple2 *apple2_create(int, int);
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extern bool apple2_is_double_video(apple2 *);
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extern int apple2_boot(apple2 *);
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extern void apple2_clear_strobe(apple2 *);
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extern void apple2_free(apple2 *);
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extern void apple2_press_key(apple2 *, vm_8bit);
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extern void apple2_release_key(apple2 *);
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extern void apple2_reset(apple2 *);
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extern void apple2_run_loop(apple2 *);
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extern void apple2_set_bank_switch(apple2 *, vm_8bit);
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extern void apple2_set_color(apple2 *, int);
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extern void apple2_set_memory_mode(apple2 *, vm_8bit);
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extern void apple2_set_video(apple2 *, int);
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#endif
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