mirror of
https://github.com/mist64/perfect6502.git
synced 2026-01-23 14:16:05 +00:00
144 lines
2.7 KiB
C
144 lines
2.7 KiB
C
#include <stdio.h>
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#ifndef _WIN32
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#include <sys/stat.h>
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#else
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#include <io.h>
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#endif
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#include "../perfect6502.h"
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state_t *state;
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/************************************************************
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*
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* Interface to OS Library Code / Monitor
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*
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************************************************************/
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/* imported by runtime.c */
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unsigned char A, X, Y, S, P;
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unsigned short PC;
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int N, Z, C;
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int
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init_monitor()
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{
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FILE *f;
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f = fopen("apple1basic/apple1basic.bin", "rb");
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if (f == NULL) {
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perror("Error opening ROM image");
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return 1;
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}
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if (fread(memory + 0xE000, 1, 4096, f) != 4096) {
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perror("Error reading ROM image");
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return 1;
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}
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fclose(f);
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memory[0xfffc] = 0x00;
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memory[0xfffd] = 0xE0;
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return 0;
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}
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void
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charout(char ch) {
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unsigned char S = readSP(state);
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unsigned short a = (1 + memory[0x0100+S+1]) | memory[0x0100+((S+2) & 0xFF)] << 8;
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/*
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* Apple I BASIC prints every character received
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* from the terminal. UNIX terminals do this
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* anyway, so we have to avoid printing every
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* line again
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*/
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if (a==0xe2a6) /* character echo */
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return;
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if (a==0xe2b6) /* CR echo */
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return;
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/*
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* Apple I BASIC prints a line break and 6 spaces
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* after every 37 characters. UNIX terminals do
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* line breaks themselves, so ignore these
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* characters
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*/
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if (a==0xe025 && (ch==10 || ch==' '))
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return;
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/* INPUT */
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if (a==0xe182) {
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#if _WIN32
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if (!_isatty(0))
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return;
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#else
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struct stat st;
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fstat(0, &st);
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if (S_ISFIFO (st.st_mode))
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return;
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#endif
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}
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putc(ch, stdout);
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fflush(stdout);
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}
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void
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handle_monitor()
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{
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if (readRW(state)) {
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unsigned short a = readAddressBus(state);
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if ((a & 0xFF1F) == 0xD010) {
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unsigned char c = getchar();
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if (c == 10)
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c = 13;
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c |= 0x80;
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writeDataBus(state, c);
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}
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if ((a & 0xFF1F) == 0xD011) {
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if (readPC(state) == 0xE006)
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/* if the code is reading a character, we have one ready */
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writeDataBus(state, 0x80);
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else
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/* if the code checks for a STOP condition, nothing is pressed */
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writeDataBus(state, 0);
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}
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if ((a & 0xFF1F) == 0xD012) {
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/* 0x80 would mean we're not yet ready to receive a character */
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writeDataBus(state, 0);
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}
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} else {
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unsigned short a = readAddressBus(state);
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unsigned char d = readDataBus(state);
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if ((a & 0xFF1F) == 0xD012) {
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unsigned char temp8 = d & 0x7F;
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if (temp8 == 13)
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temp8 = 10;
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charout(temp8);
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}
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}
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}
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int
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main(int argc, char **argv)
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{
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int clk = 0;
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state = initAndResetChip();
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/* set up memory for user program */
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if (init_monitor()) {
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return 1;
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}
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/* emulate the 6502! */
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for (;;) {
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step(state);
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clk = !clk;
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if (!clk)
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handle_monitor();
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chipStatus(state);
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//if (!(cycle % 1000)) printf("%d\n", cycle);
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};
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}
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