Improved emulation of the NRx2 write glitch (Zombie mode) on models prior to CGB-D
@@ -297,7 +297,7 @@ static void update_square_sample(GB_gameboy_t *gb, unsigned index)
requires the PCM12 register. The behavior implemented here was verified on *my*
CGB, which might behave differently from other CGB revisions, as well as from the
DMG, MGB or SGB/2 */
-static void nrx2_glitch(uint8_t *volume, uint8_t value, uint8_t old_value)
+static void _nrx2_glitch(uint8_t *volume, uint8_t value, uint8_t old_value)
{
if (value & 8) {
(*volume)++;
@@ -318,6 +318,17 @@ static void nrx2_glitch(uint8_t *volume, uint8_t value, uint8_t old_value)
(*volume) &= 0xF;
}
+static void nrx2_glitch(GB_gameboy_t *gb,uint8_t *volume, uint8_t value, uint8_t old_value)
+{
+ if (gb->model <= GB_MODEL_CGB_C) {
+ _nrx2_glitch(volume, 0xFF, old_value);
+ _nrx2_glitch(volume, value, 0xFF);
+ }
+ else {
+ _nrx2_glitch(volume, value, old_value);
+ }
+}
+
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];
@@ -931,7 +942,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
update_sample(gb, index, 0, 0);
}
else if (gb->apu.is_active[index]) {
- nrx2_glitch(&gb->apu.square_channels[index].current_volume, value, gb->io_registers[reg]);
+ nrx2_glitch(gb, &gb->apu.square_channels[index].current_volume, value, gb->io_registers[reg]);
update_square_sample(gb, index);
}
@@ -1179,7 +1190,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
update_sample(gb, GB_NOISE, 0, 0);
}
else if (gb->apu.is_active[GB_NOISE]) {
- nrx2_glitch(&gb->apu.noise_channel.current_volume, value, gb->io_registers[reg]);
+ nrx2_glitch(gb, &gb->apu.noise_channel.current_volume, value, gb->io_registers[reg]);
update_sample(gb, GB_NOISE,
gb->apu.current_lfsr_sample ?
gb->apu.noise_channel.current_volume : 0,
