155 lines
4.4 KiB
C
155 lines
4.4 KiB
C
#include <assert.h>
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#include <stdio.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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static uint8_t mem[0x10000];
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static uint8_t key = 0x80;
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static char keyString[] = "10 print \"hello\"\r20 end\rlist\rrun\r";
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static uint32_t keyCount = 0;
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static uint8_t last = 0x00;
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void prn(int c) {
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uint32_t fp;
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__asm__("movs %0, r12": "=r"(fp));
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fprintf(stderr, "### $%02x ###\n", c);
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fflush(stderr);
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__asm__("movs r12, %0":: "r"(fp));
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}
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void cpu6502_dump(uint32_t pc, uint32_t a, uint32_t x, uint32_t y,
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uint32_t sp, uint32_t sr) {
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/*
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uint32_t fp;
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__asm__("movs %0, r12": "=r"(fp));
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assert(pc < 0x10000);
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assert(a < 0x100);
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assert(x < 0x100);
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assert(y < 0x100);
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assert(sr < 0x100);
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assert(0x100 <= sp && sp < 0x200);
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fprintf(stderr, "*** dump *** PC=$%04x A=$%02x X=$%02x Y=$%02x SP=$%02x "
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"NV-B_DIZC=%d%d-%d_%d%d%d%d\n",
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pc, a, x, y, sp & 0xff, (sr >> 7) & 1, (sr >> 6) & 1, (sr >> 4) & 1,
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(sr >> 3) & 1, (sr >> 2) & 1, (sr >> 1) & 1, sr & 1);
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fflush(stderr);
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__asm__("movs r12, %0":: "r"(fp));
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*/
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}
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uint8_t cpu6502_load(uint16_t addr) {
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uint32_t fp;
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uint8_t result = 0;
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__asm__("movs %0, r12": "=r"(fp));
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if (0x0400 <= addr && addr <= 0x7ff) {
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// Fake text VRAM.
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result = mem[addr];
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result = 0xff;
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} else if ((0x0300 <= addr && addr <= 0x03ff) ||
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(0x0900 <= addr && addr <= 0x0fff)) {
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// Fake memory impl to make it run on low memory chip.
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result = last;
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} else if (0x1000 <= addr & addr < 0xbfff) {
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// Bus error due to minimum memory installation.
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return 0xff;
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fprintf(stdout, "\e[1;1Hinvalid load $%04x\n", addr);
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fflush(stdout);
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abort();
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} else if (0xc000 <= addr & addr < 0xcfff) {
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// I/O emulation.
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if (0xc000 == addr) {
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keyCount++;
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if (keyCount < 0x800) {
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result = key;
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} else if (keyCount & 0xff) {
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result = key;
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} else {
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uint32_t n = (keyCount - 0x800) >> 8;
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if (n < sizeof(keyString))
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key = keyString[n] | 0x80;
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result = key;
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}
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} else if (0xc010 == addr) {
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key &= 0x7f;
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result = 0;
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}
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} else {
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// Installed memory.
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result = mem[addr];
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}
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fprintf(stderr, "load $%04x => $%02x\n", addr, result);
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fflush(stderr);
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__asm__("movs r12, %0":: "r"(fp));
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return result;
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}
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void cpu6502_store(uint16_t addr, uint8_t data) {
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uint32_t fp;
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__asm__("movs %0, r12": "=r"(fp));
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if (0x0400 <= addr && addr <= 0x7ff) {
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// Fake text VRAM.
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char ascii[0x40] =
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"@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_ !\"#$%&'()*+,-./0123456789:;<=>?";
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mem[addr] = data;
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int y = (addr - 0x400) >> 7;
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int x = addr & 0x7f;
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if (x >= 0x50) {
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x -= 0x50;
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y += 0x10;
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} else if (x >= 0x28) {
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x -= 0x28;
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y += 0x08;
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}
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// Note: Apple2 BASIC initializes screen as:
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// 1) Fill screen with ' ' from left to right, then up to down.
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// for (var y = 0; y < 24; ++y)
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// for (var x = 0; x < 40; ++x)
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// clear x, y
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// 2) Show "APPLE ][" from back to forth.
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// 3) Count down from G to A at x = 40, y = 23
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// 4) Scroll happens on CR at line 22 or 23, right to left, up to down
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// for (var y = 0; y < 23; ++y)
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// for (var x = 39; x >= 0; --x)
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// reset x, y
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// for (var x = 0; x < 40; ++x)
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// clear x, 23
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// prompt 0, 23
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//fprintf(stdout, "\e[%d;%dH%c", y + 7, x + 1, ascii[data & 0x3f]);
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fprintf(stdout, "(%2d,%2d)@%04x%c($%02x)\n", x, y, addr, ascii[data & 0x3f], data);
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fflush(stdout);
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} else if ((0x0300 <= addr && addr <= 0x03ff) ||
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(0x0900 <= addr && addr <= 0x0fff)) {
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// Fake memory impl to make it run on low memory chip.
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last = data;
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} else if (0x1000 <= addr & addr < 0xbfff) {
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// Bus error due to minimum memory installation.
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return;
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fprintf(stdout, "\e[1;1Hinvalid store $%04x\n", addr);
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fflush(stdout);
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abort();
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} else if (0xc000 <= addr & addr < 0xcfff) {
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// I/O emulation.
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if (0xc000 == addr)
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key = data;
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} else {
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// Installed memory.
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mem[addr] = data;
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}
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fprintf(stderr, "store $%04x <= $%02x\n", addr, data);
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fflush(stderr);
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__asm__("movs r12, %0":: "r"(fp));
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}
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int main(int argc, char** argv) {
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FILE* fp = fopen("applebasic.rom", "rb");
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//FILE* fp = fopen("apple2o.rom", "rb");
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memset(mem, 0, 0x10000);
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fread(&mem[0xd000], 1, 0x3000, fp);
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fclose(fp);
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cpu6502_reset();
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fprintf(stderr, "quit: $%04x\n", cpu6502_run());
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return 0;
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}
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