57 lines
914 B
C
57 lines
914 B
C
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#include <stdint.h>
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struct cpu_flags {
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uint8_t carry : 1;
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uint8_t zero : 1;
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uint8_t interrupt_disable : 1;
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uint8_t decimal_mode : 1;
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uint8_t brk : 1;
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uint8_t unused : 1;
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uint8_t overflow : 1;
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uint8_t negative : 1;
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};
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struct registers {
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uint8_t acc, x, y, sp;
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struct cpu_flags status;
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uint16_t pc;
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};
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struct registers regs;
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enum addressing_mode {
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AM_ACCUMULATOR,
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AM_IMMEDIATE,
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AM_ZERO_PAGE,
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AM_ZERO_PAGE_X,
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AM_ZERO_PAGE_Y,
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AM_RELATIVE,
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AM_ABSOLUTE,
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AM_ABSOLUTE_X,
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AM_ABSOLUTE_Y,
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AM_INDIRECT,
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AM_INDIRECT_X,
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AM_INDIRECT_Y,
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AM_INDEXED_INDIRECT,
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AM_INDIRECT_INDEXED,
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};
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uint8_t addrbus[0x10000];
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/* example program taken from https://bugzmanov.github.io/nes_ebook/chapter_3_1.html */
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uint8_t program[] = { 0xa9, 0xc0, 0xaa, 0xe8, 0x00 };
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void interpret(void)
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{
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uint8_t opcode;
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regs.pc = 0;
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for (;;) {
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opcode = program[regs.pc++];
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switch (opcode) {
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default:
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break;
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}
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}
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}
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