uint8_t execute_interpreter_cycle(cpu_registers* registers, bool nmi_flag) {
static bool previous_nmi_flag = false;
uint8_t cpu_cycles_executed = 0;
uint8_t extra_cycles= 0;
if(DMA_is_executing()) cpu_cycles_executed = execute_DMA();
else {
uint8_t opcode = fetch_opcode(registers);
increment_PC(registers);
if(nmi_flag && !previous_nmi_flag) cpu_cycles_executed = execute_NMI(registers);
else {
#ifdef DEBUG
print_debug_info(registers, opcode);
#endif
extra_cycles = execute_instruction(registers, opcode);
cpu_cycles_executed = instruction_cycle_length[opcode] + extra_cycles;
// Do not increment PC if we jump because it will skip the first instruction at least
if(!is_JSR_or_JMP(opcode) && !is_RTI(opcode)) increment_PC_instruction_length(registers, opcode);
}
}
previous_nmi_flag = nmi_flag;
odd_cpu_cycle = cpu_cycles_executed & 0x1;
return cpu_cycles_executed;
}
void execute_loop(chip_8_cpu cpu, FILE *debug_log) {
if (pthread_create(&(cpu->delay_decrement_thread), NULL, delay_thread, cpu) != 0) {
shutdown_cpu(cpu, 1);
}
if (pthread_create(&(cpu->sound_decrement_thread), NULL, sound_thread, cpu) != 0) {
fprintf(stderr, "Failed to start the sound register thread, exiting...\n");
shutdown_cpu(cpu, 1);
}
pthread_detach(cpu->delay_decrement_thread);
pthread_detach(cpu->sound_decrement_thread);
cpu->chip_8_screen = init_ncurses(default_window_height, default_window_width);
refresh_window(cpu->chip_8_screen);
while (1) {
if (cpu->program_counter >= MEMORY_SIZE) {
fprintf(stderr, "ERR - Fatal memory error: invalid access at memory cell: '%d'\n", cpu->program_counter);
shutdown_cpu(cpu, 1);
}
if (cpu->halt) {
break;
}
opcode instr = fetch_opcode(cpu);
if (debug_log) {
print_debug_info(debug_log, instr, cpu);
}
execute_opcode(instr, cpu);
if (cpu->performed_jump) {
cpu->performed_jump = false;
continue;
}
if (cpu->skip_opcode) {
cpu->program_counter = cpu->program_counter + 2;
cpu->skip_opcode = false;
}
else {
cpu->program_counter = cpu->program_counter + 1;
}
}
// allow 0.1 seconds for the threads to clean up their memory
usleep(100000);
delwin(cpu->chip_8_screen);
endwin();
}
