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Improved emulation of NR43 writes on different revisions

This commit is contained in:
Lior Halphon 2021-01-09 21:21:22 +02:00
parent 2aa171e0ea
commit 1b3f52e8c0
1 changed files with 117 additions and 3 deletions
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120
Core/apu.c
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@ -710,6 +710,119 @@ 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)
{
uint16_t effective_counter = gb->apu.noise_channel.counter;
/* Ladies and gentlemen, I present you the holy grail glitch of revision detection! */
switch (gb->model) {
/* Pre CGB revisions are assumed to be like CGB-C, A and 0 for the lack of a better guess.
TODO: It could be verified with audio based test ROMs. */
#if 0
case GB_MODEL_CGB_B:
if (effective_counter & 8) {
effective_counter |= 0xE; // Seems to me F under some circumstances?
}
if (effective_counter & 0x80) {
effective_counter |= 0xFF;
}
if (effective_counter & 0x100) {
effective_counter |= 0x1;
}
if (effective_counter & 0x200) {
effective_counter |= 0x2;
}
if (effective_counter & 0x400) {
effective_counter |= 0x4;
}
if (effective_counter & 0x800) {
effective_counter |= 0x408;
}
if (effective_counter & 0x1000) {
effective_counter |= 0x10;
}
if (effective_counter & 0x2000) {
effective_counter |= 0x20;
}
break;
#endif
case GB_MODEL_DMG_B:
case GB_MODEL_SGB_NTSC:
case GB_MODEL_SGB_PAL:
case GB_MODEL_SGB_NTSC_NO_SFC:
case GB_MODEL_SGB_PAL_NO_SFC:
case GB_MODEL_SGB2:
case GB_MODEL_SGB2_NO_SFC:
// case GB_MODEL_CGB_0:
// case GB_MODEL_CGB_A:
case GB_MODEL_CGB_C:
if (effective_counter & 8) {
effective_counter |= 0xE;
}
if (effective_counter & 0x80) {
effective_counter |= 0xFF;
}
if (effective_counter & 0x100) {
effective_counter |= 0x1;
}
if (effective_counter & 0x200) {
effective_counter |= 0x2;
}
if (effective_counter & 0x400) {
effective_counter |= 0x4;
}
if (effective_counter & 0x800) {
effective_counter |= 0x8;
}
if (effective_counter & 0x1000) {
effective_counter |= 0x10;
}
if (effective_counter & 0x2000) {
effective_counter |= 0x20;
}
break;
#if 0
case GB_MODEL_CGB_D:
if (effective_counter & 0x40) {
effective_counter |= 0xFF;
}
if (effective_counter & 0x100) {
effective_counter |= 0x1;
}
if (effective_counter & 0x200) {
effective_counter |= 0x2;
}
if (effective_counter & 0x400) {
effective_counter |= 0x4;
}
if (effective_counter & 0x800) {
effective_counter |= 0x8;
}
if (effective_counter & 0x1000) {
effective_counter |= 0x10;
}
break;
#endif
case GB_MODEL_CGB_E:
if (effective_counter & 0x40) {
effective_counter |= 0xFF;
}
if (effective_counter & 0x1000) {
effective_counter |= 0x10;
}
break;
case GB_MODEL_AGB:
/* TODO: AGBs are not affected, but AGSes are. They don't seem to follow a simple
pattern like the other revisions. */
/* For the most part, AGS seems to do:
0x20 -> 0xA0
0x200 -> 0xA00
0x1000 -> 0x1010
*/
break;
}
return effective_counter;
}
void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
{
if (!gb->apu.global_enable && reg != GB_IO_NR52 && reg < GB_IO_WAV_START && (GB_is_cgb(gb) ||
@ -1068,9 +1181,10 @@ 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;
bool old_bit = (gb->apu.noise_channel.counter >> (gb->io_registers[GB_IO_NR43] >> 4)) & 1;
uint16_t effective_counter = effective_channel4_counter(gb);
bool old_bit = (effective_counter >> (gb->io_registers[GB_IO_NR43] >> 4)) & 1;
gb->io_registers[GB_IO_NR43] = value;
bool new_bit = (gb->apu.noise_channel.counter >> (gb->io_registers[GB_IO_NR43] >> 4)) & 1;
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;
@ -1079,7 +1193,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
gb->apu.channel_4_delta = 0;
}
/* Step LFSR */
if (new_bit && !old_bit) {
if (new_bit && (!old_bit || gb->model <= GB_MODEL_CGB_C)) {
step_lfsr(gb, 0);
}
break;