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More correct emulation of manual clocking of channels 1 and 2

This commit is contained in:
Lior Halphon 2021-02-22 15:27:17 +02:00
parent 71c88323b7
commit 8809d8ac2f
1 changed files with 9 additions and 8 deletions
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17
Core/apu.c
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@ -1000,16 +1000,17 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
else {
unsigned extra_delay = 0;
if (gb->model == GB_MODEL_CGB_E /* || gb->model == GB_MODEL_CGB_D */) {
if ((!(value & 4) && ((gb->io_registers[reg] & 4) || old_sample_length == 0x3FF)) ||
(old_sample_length == 0x7FF && gb->apu.square_channels[index].sample_length != 0x7FF)) {
if (!(value & 4) && !(((gb->apu.square_channels[index].sample_countdown - 1) / 2) & 0x400)) {
gb->apu.square_channels[index].current_sample_index++;
gb->apu.square_channels[index].current_sample_index &= 0x7;
}
else if (gb->apu.square_channels[index].sample_length == 0x7FF &&
old_sample_length != 0x7FF &&
(gb->apu.square_channels[index].current_sample_index & 0x80)) {
extra_delay += 2;
}
gb->apu.is_active[index] = true;
}
/* Todo: verify with the schematics what's going on in here */
else if (gb->apu.square_channels[index].sample_length == 0x7FF &&
old_sample_length != 0x7FF &&
(gb->apu.square_channels[index].current_sample_index & 0x80)) {
extra_delay += 2;
}
}
/* Timing quirk: if already active, sound starts 2 (2MHz) ticks earlier.*/
gb->apu.square_channels[index].sample_countdown = (gb->apu.square_channels[index].sample_length ^ 0x7FF) * 2 + 4 - gb->apu.lf_div + extra_delay;