diff --git a/Core/apu.c b/Core/apu.c index 3706599..bd00d49 100644 --- a/Core/apu.c +++ b/Core/apu.c @@ -710,7 +710,7 @@ uint8_t GB_apu_read(GB_gameboy_t *gb, uint8_t reg) return gb->io_registers[reg] | read_mask[reg - GB_IO_NR10]; } -static inline uint16_t effective_channel4_counter(GB_gameboy_t *gb) +static inline uint16_t effective_channel4_counter(GB_gameboy_t *gb, uint8_t nr43) { uint16_t effective_counter = gb->apu.noise_channel.counter; /* Ladies and gentlemen, I present you the holy grail glitch of revision detection! */ @@ -720,7 +720,14 @@ static inline uint16_t effective_channel4_counter(GB_gameboy_t *gb) #if 0 case GB_MODEL_CGB_B: if (effective_counter & 8) { - effective_counter |= 0xE; // Seems to me F under some circumstances? + // Verify this part + if (gb->apu.channel_4_countdown_reloaded && !(effective_counter & 1)) { + uint16_t lower_bits = ~(effective_counter & ~(effective_counter - 1)) & 0xF; + effective_counter = (effective_counter & ~0xF) | lower_bits; + } + else { + effective_counter |= 0xF; + } } if (effective_counter & 0x80) { effective_counter |= 0xFF; @@ -756,7 +763,16 @@ static inline uint16_t effective_channel4_counter(GB_gameboy_t *gb) // case GB_MODEL_CGB_A: case GB_MODEL_CGB_C: if (effective_counter & 8) { - effective_counter |= 0xE; + if (gb->apu.channel_4_countdown_reloaded && !(effective_counter & 1)) { + uint16_t lower_bits = ~(effective_counter & ~(effective_counter - 1)) & 0xF; + effective_counter = (effective_counter & ~0xF) | lower_bits; + if (!(nr43 >> 4)) { + effective_counter &= ~1; + } + } + else { + effective_counter |= 0xE; + } } if (effective_counter & 0x80) { effective_counter |= 0xFF; @@ -820,6 +836,9 @@ static inline uint16_t effective_channel4_counter(GB_gameboy_t *gb) */ break; } + if (gb->model <= GB_MODEL_CGB_C && gb->apu.channel_4_countdown_reloaded && (nr43 >> 4)) { + effective_counter = (effective_counter & effective_counter - 1) | (effective_counter & 1); + } return effective_counter; } @@ -1181,16 +1200,22 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value) case GB_IO_NR43: { gb->apu.noise_channel.narrow = value & 8; - uint16_t effective_counter = effective_channel4_counter(gb); + uint16_t effective_counter = effective_channel4_counter(gb, value); bool old_bit = (effective_counter >> (gb->io_registers[GB_IO_NR43] >> 4)) & 1; gb->io_registers[GB_IO_NR43] = value; bool new_bit = (effective_counter >> (gb->io_registers[GB_IO_NR43] >> 4)) & 1; if (gb->apu.channel_4_countdown_reloaded) { unsigned divisor = (gb->io_registers[GB_IO_NR43] & 0x07) << 2; if (!divisor) divisor = 2; - gb->apu.noise_channel.counter_countdown = - divisor + (divisor == 2? 0 : (uint8_t[]){2, 1, 0, 3}[(gb->apu.noise_channel.alignment) & 3]); - gb->apu.channel_4_delta = 0; + if (gb->model > GB_MODEL_CGB_C) { + gb->apu.noise_channel.counter_countdown = + divisor + (divisor == 2? 0 : (uint8_t[]){2, 1, 0, 3}[(gb->apu.noise_channel.alignment) & 3]); + } + else { + gb->apu.noise_channel.counter_countdown = + divisor + (divisor == 2? 0 : (uint8_t[]){2, 1, 4, 3}[(gb->apu.noise_channel.alignment) & 3]); + } + gb->apu.channel_4_delta = 0; } /* Step LFSR */ if (new_bit && (!old_bit || gb->model <= GB_MODEL_CGB_C)) { @@ -1238,15 +1263,6 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value) } } - /* TODO: These two are quite weird. Verify further */ - if (gb->model <= GB_MODEL_CGB_C && gb->cgb_double_speed) { - if (!(gb->io_registers[GB_IO_NR43] & 0xF0) && (gb->io_registers[GB_IO_NR43] & 0x07)) { - gb->apu.noise_channel.counter_countdown -= 1; - } - else if ((gb->io_registers[GB_IO_NR43] & 0xF0) && !(gb->io_registers[GB_IO_NR43] & 0x07)) { - gb->apu.noise_channel.counter_countdown += 1; - } - } gb->apu.noise_channel.current_volume = gb->io_registers[GB_IO_NR42] >> 4;