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Correct emulation of enabling and disabling the volume envelope. Correct emulation of a glitch where the volume envelope ticks when it usually wouldn’t.

This commit is contained in:
Lior Halphon 2018-09-10 16:59:59 +03:00
parent 3151821e6d
commit ec0a879a93
1 changed files with 70 additions and 40 deletions
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110
Core/apu.c
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@ -177,6 +177,55 @@ static void nrx2_glitch(uint8_t *volume, uint8_t value, uint8_t old_value)
(*volume) &= 0xF;
}
static void tick_square_envelope(GB_gameboy_t *gb, enum GB_CHANNELS index)
{
uint8_t nrx2 = gb->io_registers[index == GB_SQUARE_1? GB_IO_NR12 : GB_IO_NR22];
if (gb->apu.square_channels[index].volume_countdown || (nrx2 & 7)) {
if (!gb->apu.square_channels[index].volume_countdown || !--gb->apu.square_channels[index].volume_countdown) {
if ((nrx2 & 8) && gb->apu.square_channels[index].current_volume < 0xF) {
gb->apu.square_channels[index].current_volume++;
}
else if (!(nrx2 & 8) && gb->apu.square_channels[index].current_volume > 0) {
gb->apu.square_channels[index].current_volume--;
}
gb->apu.square_channels[index].volume_countdown = nrx2 & 7;
if (gb->apu.is_active[index]) {
update_square_sample(gb, index);
}
}
}
}
static void tick_noise_envelope(GB_gameboy_t *gb)
{
uint8_t nr42 = gb->io_registers[GB_IO_NR42];
if (gb->apu.noise_channel.volume_countdown || (nr42 & 7)) {
if (!--gb->apu.noise_channel.volume_countdown) {
if ((nr42 & 8) && gb->apu.noise_channel.current_volume < 0xF) {
gb->apu.noise_channel.current_volume++;
}
else if (!(nr42 & 8) && gb->apu.noise_channel.current_volume > 0) {
gb->apu.noise_channel.current_volume--;
}
gb->apu.noise_channel.volume_countdown = nr42 & 7;
if (gb->apu.is_active[GB_NOISE]) {
update_sample(gb, GB_NOISE,
(gb->apu.noise_channel.lfsr & 1) ?
gb->apu.noise_channel.current_volume : 0,
0);
}
}
}
}
void GB_apu_div_event(GB_gameboy_t *gb)
{
if (!gb->apu.global_enable) return;
@ -186,53 +235,27 @@ void GB_apu_div_event(GB_gameboy_t *gb)
}
gb->apu.div_divider++;
if ((gb->apu.div_divider & 7) == 0) {
if ((gb->apu.div_divider & 1) == 0) {
for (unsigned i = GB_SQUARE_2 + 1; i--;) {
uint8_t nrx2 = gb->io_registers[i == GB_SQUARE_1? GB_IO_NR12 : GB_IO_NR22];
if (gb->apu.square_channels[i].volume_countdown) {
if (!--gb->apu.square_channels[i].volume_countdown) {
if ((nrx2 & 8) && gb->apu.square_channels[i].current_volume < 0xF) {
gb->apu.square_channels[i].current_volume++;
}
else if (!(nrx2 & 8) && gb->apu.square_channels[i].current_volume > 0) {
gb->apu.square_channels[i].current_volume--;
}
gb->apu.square_channels[i].volume_countdown = nrx2 & 7;
if (gb->apu.is_active[i]) {
update_square_sample(gb, i);
}
}
if (gb->apu.is_active[i] && gb->apu.square_channels[i].volume_countdown == 0 && (nrx2 & 7)) {
tick_square_envelope(gb, i);
}
}
uint8_t nr42 = gb->io_registers[GB_IO_NR42];
if (gb->apu.noise_channel.volume_countdown) {
if (!--gb->apu.noise_channel.volume_countdown) {
if ((nr42 & 8) && gb->apu.noise_channel.current_volume < 0xF) {
gb->apu.noise_channel.current_volume++;
}
else if (!(nr42 & 8) && gb->apu.noise_channel.current_volume > 0) {
gb->apu.noise_channel.current_volume--;
}
gb->apu.noise_channel.volume_countdown = nr42 & 7;
if (gb->apu.is_active[GB_NOISE]) {
update_sample(gb, GB_NOISE,
(gb->apu.noise_channel.lfsr & 1) ?
gb->apu.noise_channel.current_volume : 0,
0);
}
}
if (gb->apu.is_active[GB_NOISE] && gb->apu.noise_channel.volume_countdown && (gb->io_registers[GB_IO_NR42] & 7)) {
tick_noise_envelope(gb);
}
}
if ((gb->apu.div_divider & 7) == 0) {
for (unsigned i = GB_SQUARE_2 + 1; i--;) {
tick_square_envelope(gb, i);
}
tick_noise_envelope(gb);
}
if ((gb->apu.div_divider & 1) == 1) {
for (unsigned i = GB_SQUARE_2 + 1; i--;) {
if (gb->apu.square_channels[i].length_enabled) {
@ -589,6 +612,10 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
case GB_IO_NR12:
case GB_IO_NR22: {
unsigned index = reg == GB_IO_NR22? GB_SQUARE_2: GB_SQUARE_1;
if (((value & 0x7) == 0) && ((gb->io_registers[reg] & 0x7) != 0)) {
/* Envelope disabled */
gb->apu.square_channels[index].volume_countdown = 0;
}
if ((value & 0xF8) == 0) {
/* According to Blargg's test ROM this should disable the channel instantly
TODO: verify how "instant" the change is using PCM12 */
@ -785,7 +812,10 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
}
case GB_IO_NR42: {
if (((value & 0x7) == 0) && ((gb->io_registers[reg] & 0x7) != 0)) {
/* Envelope disabled */
gb->apu.noise_channel.volume_countdown = 0;
}
if ((value & 0xF8) == 0) {
/* According to Blargg's test ROM this should disable the channel instantly
TODO: verify how "instant" the change is using PCM12 */