mirror of
https://github.com/libretro/bsnes-libretro.git
synced 2024-12-01 04:51:10 +00:00
257 lines
7.6 KiB
C
257 lines
7.6 KiB
C
#include "gb.h"
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#ifdef _WIN32
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#define _WIN32_WINNT 0x0500
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#include <Windows.h>
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#else
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#include <sys/time.h>
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#endif
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static const unsigned int GB_TAC_RATIOS[] = {1024, 16, 64, 256};
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#ifndef DISABLE_TIMEKEEPING
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static int64_t get_nanoseconds(void)
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{
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#ifndef _WIN32
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struct timeval now;
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gettimeofday(&now, NULL);
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return (now.tv_usec) * 1000 + now.tv_sec * 1000000000L;
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#else
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FILETIME time;
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GetSystemTimeAsFileTime(&time);
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return (((int64_t)time.dwHighDateTime << 32) | time.dwLowDateTime) * 100L;
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#endif
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}
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static void nsleep(uint64_t nanoseconds)
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{
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#ifndef _WIN32
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struct timespec sleep = {0, nanoseconds};
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nanosleep(&sleep, NULL);
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#else
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HANDLE timer;
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LARGE_INTEGER time;
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timer = CreateWaitableTimer(NULL, true, NULL);
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time.QuadPart = -(nanoseconds / 100L);
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SetWaitableTimer(timer, &time, 0, NULL, NULL, false);
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WaitForSingleObject(timer, INFINITE);
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CloseHandle(timer);
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#endif
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}
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bool GB_timing_sync_turbo(GB_gameboy_t *gb)
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{
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if (!gb->turbo_dont_skip) {
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int64_t nanoseconds = get_nanoseconds();
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if (nanoseconds <= gb->last_sync + (1000000000LL * LCDC_PERIOD / GB_get_clock_rate(gb))) {
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return true;
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}
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gb->last_sync = nanoseconds;
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}
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return false;
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}
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void GB_timing_sync(GB_gameboy_t *gb)
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{
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if (gb->turbo) {
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gb->cycles_since_last_sync = 0;
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return;
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}
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/* Prevent syncing if not enough time has passed.*/
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if (gb->cycles_since_last_sync < LCDC_PERIOD / 4) return;
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uint64_t target_nanoseconds = gb->cycles_since_last_sync * 1000000000LL / 2 / GB_get_clock_rate(gb); /* / 2 because we use 8MHz units */
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int64_t nanoseconds = get_nanoseconds();
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if (labs((signed long)(nanoseconds - gb->last_sync)) < target_nanoseconds ) {
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nsleep(target_nanoseconds + gb->last_sync - nanoseconds);
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gb->last_sync += target_nanoseconds;
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}
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else {
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gb->last_sync = nanoseconds;
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}
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gb->cycles_since_last_sync = 0;
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}
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#else
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bool GB_timing_sync_turbo(GB_gameboy_t *gb)
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{
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return false;
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}
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void GB_timing_sync(GB_gameboy_t *gb)
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{
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}
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#endif
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static void GB_ir_run(GB_gameboy_t *gb)
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{
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if (gb->ir_queue_length == 0) return;
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if (gb->cycles_since_input_ir_change >= gb->ir_queue[0].delay) {
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gb->cycles_since_input_ir_change -= gb->ir_queue[0].delay;
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gb->infrared_input = gb->ir_queue[0].state;
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gb->ir_queue_length--;
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memmove(&gb->ir_queue[0], &gb->ir_queue[1], sizeof(gb->ir_queue[0]) * (gb->ir_queue_length));
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}
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}
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static void advance_tima_state_machine(GB_gameboy_t *gb)
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{
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if (gb->tima_reload_state == GB_TIMA_RELOADED) {
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gb->tima_reload_state = GB_TIMA_RUNNING;
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}
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else if (gb->tima_reload_state == GB_TIMA_RELOADING) {
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gb->io_registers[GB_IO_IF] |= 4;
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gb->tima_reload_state = GB_TIMA_RELOADED;
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}
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}
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static bool counter_overflow_check(uint32_t old, uint32_t new, uint32_t max)
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{
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return (old & (max >> 1)) && !(new & (max >> 1));
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}
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static void increase_tima(GB_gameboy_t *gb)
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{
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gb->io_registers[GB_IO_TIMA]++;
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if (gb->io_registers[GB_IO_TIMA] == 0) {
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gb->io_registers[GB_IO_TIMA] = gb->io_registers[GB_IO_TMA];
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gb->tima_reload_state = GB_TIMA_RELOADING;
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}
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}
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static void GB_set_internal_div_counter(GB_gameboy_t *gb, uint32_t value)
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{
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/* TIMA increases when a specific high-bit becomes a low-bit. */
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value &= INTERNAL_DIV_CYCLES - 1;
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if ((gb->io_registers[GB_IO_TAC] & 4) &&
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counter_overflow_check(gb->div_counter, value, GB_TAC_RATIOS[gb->io_registers[GB_IO_TAC] & 3])) {
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increase_tima(gb);
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}
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if (counter_overflow_check(gb->div_counter, value, gb->cgb_double_speed? 0x4000 : 0x2000)) {
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GB_apu_run(gb);
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GB_apu_div_event(gb);
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}
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gb->div_counter = value;
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}
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static void GB_timers_run(GB_gameboy_t *gb, uint8_t cycles)
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{
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GB_STATE_MACHINE(gb, div, cycles, 1) {
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GB_STATE(gb, div, 1);
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GB_STATE(gb, div, 2);
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}
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GB_set_internal_div_counter(gb, 0);
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GB_SLEEP(gb, div, 1, 2);
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while (true) {
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advance_tima_state_machine(gb);
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GB_set_internal_div_counter(gb, gb->div_counter + 4);
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gb->apu.apu_cycles += 4 << !gb->cgb_double_speed;
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GB_SLEEP(gb, div, 2, 4);
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}
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}
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void GB_advance_cycles(GB_gameboy_t *gb, uint8_t cycles)
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{
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/* It appears that on the CGB, write timing is a bit different then on the DMG, effectively
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making writes 1 T-cycle late when compared to the DMG. */
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if (gb->is_cgb) {
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cycles = (cycles + 1) & ~3;
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if (cycles == 0) return;
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}
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// Affected by speed boost
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gb->dma_cycles += cycles;
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GB_timers_run(gb, cycles);
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uint16_t previous_serial_cycles = gb->serial_cycles;
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gb->serial_cycles += cycles;
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if (gb->serial_length) {
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if ((gb->serial_cycles & gb->serial_length) != (previous_serial_cycles & gb->serial_length)) {
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gb->serial_length = 0;
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gb->io_registers[GB_IO_SC] &= ~0x80;
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/* TODO: Does SB "update" bit by bit? */
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if (gb->serial_transfer_end_callback) {
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gb->io_registers[GB_IO_SB] = gb->serial_transfer_end_callback(gb);
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}
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else {
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gb->io_registers[GB_IO_SB] = 0xFF;
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}
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gb->io_registers[GB_IO_IF] |= 8;
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}
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}
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gb->debugger_ticks += cycles;
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if (!gb->cgb_double_speed) {
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cycles <<= 1;
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}
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// Not affected by speed boost
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gb->hdma_cycles += cycles;
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gb->apu_output.sample_cycles += cycles;
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gb->cycles_since_ir_change += cycles;
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gb->cycles_since_input_ir_change += cycles;
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gb->cycles_since_last_sync += cycles;
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gb->cycles_since_run += cycles;
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GB_dma_run(gb);
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GB_hdma_run(gb);
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GB_apu_run(gb);
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GB_display_run(gb, cycles);
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GB_ir_run(gb);
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}
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/*
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This glitch is based on the expected results of mooneye-gb rapid_toggle test.
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This glitch happens because how TIMA is increased, see GB_set_internal_div_counter.
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According to GiiBiiAdvance, GBC's behavior is different, but this was not tested or implemented.
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*/
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void GB_emulate_timer_glitch(GB_gameboy_t *gb, uint8_t old_tac, uint8_t new_tac)
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{
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/* Glitch only happens when old_tac is enabled. */
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if (!(old_tac & 4)) return;
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unsigned int old_clocks = GB_TAC_RATIOS[old_tac & 3];
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unsigned int new_clocks = GB_TAC_RATIOS[new_tac & 3];
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/* The bit used for overflow testing must have been 1 */
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if (gb->div_counter & (old_clocks >> 1)) {
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/* And now either the timer must be disabled, or the new bit used for overflow testing be 0. */
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if (!(new_tac & 4) || gb->div_counter & (new_clocks >> 1)) {
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increase_tima(gb);
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}
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}
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}
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void GB_rtc_run(GB_gameboy_t *gb)
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{
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if ((gb->rtc_real.high & 0x40) == 0) { /* is timer running? */
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time_t current_time = time(NULL);
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while (gb->last_rtc_second < current_time) {
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gb->last_rtc_second++;
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if (++gb->rtc_real.seconds == 60)
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{
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gb->rtc_real.seconds = 0;
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if (++gb->rtc_real.minutes == 60)
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{
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gb->rtc_real.minutes = 0;
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if (++gb->rtc_real.hours == 24)
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{
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gb->rtc_real.hours = 0;
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if (++gb->rtc_real.days == 0)
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{
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if (gb->rtc_real.high & 1) /* Bit 8 of days*/
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{
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gb->rtc_real.high |= 0x80; /* Overflow bit */
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}
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gb->rtc_real.high ^= 1;
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}
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}
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}
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}
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}
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}
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}
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