mirror of https://github.com/jborza/emu6502.git
74 lines
1.6 KiB
C
74 lines
1.6 KiB
C
#include "state.h"
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#include "cpu.h"
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#include "opcodes.h"
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#include <stdio.h>
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void* unimplemented_instruction(State6502* state) {
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printf("Error: unimplemented instruction\n");
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exit(1);
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}
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void set_NV_flags(State6502* state, word value) {
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//if(value)
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}
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void clear_flags(State6502* state) {
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memcpy(&state->flags, &state->a,1);
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}
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void clear_state(State6502* state) {
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state->a = 0;
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state->x = 0;
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state->y = 0;
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state->pc = 0;
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state->sp = 0;
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//state -> flags = (Flags)0;
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clear_flags(state);
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state->running = 1;
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}
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byte pop_byte(State6502* state) {
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return state->memory[state->pc++];
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}
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void print_state(State6502* state) {
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printf("\tC=%d,Z=%d,I=%d,D=%d,B=%d,V=%d,N=%d\n", state->flags.c, state->flags.z, state->flags.i, state->flags.d, state->flags.b, state->flags.v, state->flags.n);
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printf("\tA $%02x X $%02x Y $%02x SP $%02x PC $%04x\n", state->a, state->x, state->y, state->sp, state->pc);
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}
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void print_memory(State6502* state, word offset) {
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printf("$%04x: ", offset);
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for (byte i = 0; i < 32; i++) {
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printf("%02x", state->memory[offset + i]);
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if (i % 8 == 7)
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printf("|");
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else
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printf(" ");
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}
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printf("\n");
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}
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//bitwise or with accumulator
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void ORA(State6502 * state, byte operand) {
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word result = state->a | operand;
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set_NV_flags(state, result);
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state->a = result & 0xff;
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}
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int emulate_6502_op(State6502 * state) {
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byte* opcode = &state->memory[state->pc++];
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switch (*opcode) {
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case 0x00: break; //NOP
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case 0x01: //ORA, indirect, x
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break;
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case 0x05: //ORA, zero page
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byte zp = pop_byte(state);
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ORA(state, state->memory[zp]);
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break;
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case 0x09: //ORA
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default:
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unimplemented_instruction(state); break;
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}
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return 0;
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}
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