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T6W28: fix noise emulation

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thanks to Burnt Fishy and The Beesh-Spweesh! for information
This commit is contained in:
tildearrow 2025-08-19 20:58:08 -05:00
parent 3b37a5334a
commit ee64dd6a16
3 changed files with 13 additions and 9 deletions
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18
src/engine/platform/sound/t6w28/T6W28_Apu.cpp
View file

@ -145,8 +145,8 @@ static const int noise_periods [3] = { 0x100, 0x200, 0x400 };
void T6W28_Noise::reset() void T6W28_Noise::reset()
{ {
period = &noise_periods [0]; period = &noise_periods [0];
shifter = 0x4000; shifter = 0xfffe;
tap = 13; tap = 12;
period_extra = 0; period_extra = 0;
T6W28_Osc::reset(); T6W28_Osc::reset();
} }
@ -201,9 +201,13 @@ void T6W28_Noise::run( sms_time_t time, sms_time_t end_time )
do do
{ {
int changed = (l_shifter + 1) & 2; // set if prev and next bits differ int prev_l_shifter=l_shifter;
l_shifter = (((l_shifter << 14) ^ (l_shifter << tap)) & 0x4000) | (l_shifter >> 1); if (tap==16) {
if ( changed ) l_shifter = ((l_shifter >> 14) & 1) | (l_shifter << 1);
} else {
l_shifter = ((((l_shifter >> 15)&1) ^ ((l_shifter >> 12)&1)) & 1) | (l_shifter << 1);
}
if ( (prev_l_shifter^l_shifter)&1 )
{ {
delta_left = -delta_left; delta_left = -delta_left;
blip_add_delta( output_left, time, delta_left ); blip_add_delta( output_left, time, delta_left );
@ -370,8 +374,8 @@ void T6W28_Apu::write_data_right( sms_time_t time, int data )
noise.period = &noise.period_extra; noise.period = &noise.period_extra;
int const tap_disabled = 16; int const tap_disabled = 16;
noise.tap = (data & 0x04) ? 13 : tap_disabled; noise.tap = (data & 0x04) ? 12 : tap_disabled;
noise.shifter = 0x4000; noise.shifter = 0xfffe;
} }
} }

2
src/gui/about.cpp
View file

@ -146,7 +146,7 @@ const char* aboutLine[]={
_N("MAME µPD1771C-017 HLE core by David Viens"), _N("MAME µPD1771C-017 HLE core by David Viens"),
_N("SAASound by Dave Hooper and Simon Owen"), _N("SAASound by Dave Hooper and Simon Owen"),
_N("SameBoy by Lior Halphon"), _N("SameBoy by Lior Halphon"),
_N("Mednafen PCE, WonderSwan, T6W28 and Virtual Boy audio cores"), _N("Mednafen PCE, WonderSwan, T6W28 (modified) and Virtual Boy audio cores"),
_N("WonderSwan new core by asiekierka"), _N("WonderSwan new core by asiekierka"),
_N("SNES DSP core by Blargg"), _N("SNES DSP core by Blargg"),
_N("puNES (NES, MMC5 and FDS) by FHorse (modified version)"), _N("puNES (NES, MMC5 and FDS) by FHorse (modified version)"),

2
src/main.cpp
View file

@ -327,7 +327,7 @@ TAParamResult pVersion(String) {
printf("- SAASound by Dave Hooper and Simon Owen (BSD 3-clause)\n"); printf("- SAASound by Dave Hooper and Simon Owen (BSD 3-clause)\n");
printf("- SameBoy by Lior Halphon (MIT)\n"); printf("- SameBoy by Lior Halphon (MIT)\n");
printf("- Mednafen PCE, WonderSwan and Virtual Boy by Mednafen Team (GPLv2)\n"); printf("- Mednafen PCE, WonderSwan and Virtual Boy by Mednafen Team (GPLv2)\n");
printf("- Mednafen T6W28 by Blargg (GPLv2)\n"); printf("- Mednafen T6W28 (modified version) by Blargg (GPLv2)\n");
printf("- WonderSwan new core by asiekierka (zlib license)\n"); printf("- WonderSwan new core by asiekierka (zlib license)\n");
printf("- SNES DSP core by Blargg (LGPLv2.1)\n"); printf("- SNES DSP core by Blargg (LGPLv2.1)\n");
printf("- puNES (modified version) by FHorse (GPLv2)\n"); printf("- puNES (modified version) by FHorse (GPLv2)\n");