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Emulate the delayed NR44 write on the DMG

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This commit is contained in:
Lior Halphon 2020-12-12 18:11:35 +02:00
parent 6b30de5fb1
commit dffc12331b
1 changed files with 59 additions and 35 deletions
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94
Core/apu.c
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@ -451,6 +451,22 @@ void GB_apu_run(GB_gameboy_t *gb)
uint8_t cycles = gb->apu.apu_cycles >> 2; uint8_t cycles = gb->apu.apu_cycles >> 2;
gb->apu.apu_cycles = 0; gb->apu.apu_cycles = 0;
if (!cycles) return; if (!cycles) return;
bool start_ch4 = false;
if (gb->apu.channel_4_dmg_delayed_start) {
if (gb->apu.channel_4_dmg_delayed_start == cycles) {
gb->apu.channel_4_dmg_delayed_start = 0;
start_ch4 = true;
}
else if (gb->apu.channel_4_dmg_delayed_start > cycles) {
gb->apu.channel_4_dmg_delayed_start -= cycles;
}
else {
/* Split it into two */
cycles -= gb->apu.channel_4_dmg_delayed_start;
gb->apu.apu_cycles = gb->apu.channel_4_dmg_delayed_start * 2;
GB_apu_run(gb);
}
}
if (likely(!gb->stopped || GB_is_cgb(gb))) { if (likely(!gb->stopped || GB_is_cgb(gb))) {
/* To align the square signal to 1MHz */ /* To align the square signal to 1MHz */
@ -572,6 +588,9 @@ void GB_apu_run(GB_gameboy_t *gb)
render(gb); render(gb);
} }
} }
if (start_ch4) {
GB_apu_write(gb, GB_IO_NR44, gb->io_registers[GB_IO_NR44] | 0x80);
}
} }
void GB_apu_init(GB_gameboy_t *gb) void GB_apu_init(GB_gameboy_t *gb)
{ {
@ -978,49 +997,54 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
case GB_IO_NR44: { case GB_IO_NR44: {
if (value & 0x80) { if (value & 0x80) {
unsigned divisor = (gb->io_registers[GB_IO_NR43] & 0x07) << 2; if (!GB_is_cgb(gb) && (gb->apu.noise_channel.alignment & 3) != 0) {
if (!divisor) divisor = 2; gb->apu.channel_4_dmg_delayed_start = 6;
gb->apu.channel_4_delta = 0;
gb->apu.noise_channel.counter_countdown = divisor + 4;
if (divisor == 2) {
gb->apu.noise_channel.counter_countdown += 1 - gb->apu.lf_div;
} }
else { else {
gb->apu.noise_channel.counter_countdown += (uint8_t[]){2, 1, 0, 3}[gb->apu.noise_channel.alignment & 3]; unsigned divisor = (gb->io_registers[GB_IO_NR43] & 0x07) << 2;
if (((gb->apu.noise_channel.alignment + 1) & 3) < 2) { if (!divisor) divisor = 2;
if ((gb->io_registers[GB_IO_NR43] & 0x07) == 1) { gb->apu.channel_4_delta = 0;
gb->apu.noise_channel.counter_countdown -= 2; gb->apu.noise_channel.counter_countdown = divisor + 4;
gb->apu.channel_4_delta = 2; if (divisor == 2) {
} gb->apu.noise_channel.counter_countdown += 1 - gb->apu.lf_div;
else { }
gb->apu.noise_channel.counter_countdown -= 4; else {
gb->apu.noise_channel.counter_countdown += (uint8_t[]){2, 1, 0, 3}[gb->apu.noise_channel.alignment & 3];
if (((gb->apu.noise_channel.alignment + 1) & 3) < 2) {
if ((gb->io_registers[GB_IO_NR43] & 0x07) == 1) {
gb->apu.noise_channel.counter_countdown -= 2;
gb->apu.channel_4_delta = 2;
}
else {
gb->apu.noise_channel.counter_countdown -= 4;
}
} }
} }
}
gb->apu.noise_channel.current_volume = gb->io_registers[GB_IO_NR42] >> 4; gb->apu.noise_channel.current_volume = gb->io_registers[GB_IO_NR42] >> 4;
/* The volume changes caused by NRX4 sound start take effect instantly (i.e. the effect the previously /* The volume changes caused by NRX4 sound start take effect instantly (i.e. the effect the previously
started sound). The playback itself is not instant which is why we don't update the sample for other started sound). The playback itself is not instant which is why we don't update the sample for other
cases. */ cases. */
if (gb->apu.is_active[GB_NOISE]) { if (gb->apu.is_active[GB_NOISE]) {
update_sample(gb, GB_NOISE, update_sample(gb, GB_NOISE,
gb->apu.current_lfsr_sample ? gb->apu.current_lfsr_sample ?
gb->apu.noise_channel.current_volume : 0, gb->apu.noise_channel.current_volume : 0,
0); 0);
} }
gb->apu.noise_channel.lfsr = 0; gb->apu.noise_channel.lfsr = 0;
gb->apu.current_lfsr_sample = false; gb->apu.current_lfsr_sample = false;
gb->apu.noise_channel.volume_countdown = gb->io_registers[GB_IO_NR42] & 7; gb->apu.noise_channel.volume_countdown = gb->io_registers[GB_IO_NR42] & 7;
if (!gb->apu.is_active[GB_NOISE] && (gb->io_registers[GB_IO_NR42] & 0xF8) != 0) { if (!gb->apu.is_active[GB_NOISE] && (gb->io_registers[GB_IO_NR42] & 0xF8) != 0) {
gb->apu.is_active[GB_NOISE] = true; gb->apu.is_active[GB_NOISE] = true;
update_sample(gb, GB_NOISE, 0, 0); update_sample(gb, GB_NOISE, 0, 0);
} }
if (gb->apu.noise_channel.pulse_length == 0) { if (gb->apu.noise_channel.pulse_length == 0) {
gb->apu.noise_channel.pulse_length = 0x40; gb->apu.noise_channel.pulse_length = 0x40;
gb->apu.noise_channel.length_enabled = false; gb->apu.noise_channel.length_enabled = false;
}
} }
} }