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AY8930: Fix tone and noise period in expanded mode. 

By doubling the internal clock frequency.

In expanded mode, the same tone period is an octave higher than in compat mode.
In expanded mode, the noise period is twice as fast as currently implemented.

See https://github.com/tildearrow/furnace/pull/416
This commit is contained in:
Laurens Holst 2022-05-03 19:32:17 +02:00
parent ffa0727bf6
commit 49ff39abee
2 changed files with 6 additions and 6 deletions
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4
src/engine/platform/ay8930.cpp
View File

@ -27,7 +27,7 @@
#define rWrite(a,v) if (!skipRegisterWrites) {pendingWrites[a]=v;}
#define immWrite2(a,v) if (!skipRegisterWrites) {writes.emplace(a,v); if (dumpWrites) {addWrite(a,v);} }
#define CHIP_DIVIDER 8
#define CHIP_DIVIDER 4
const char* regCheatSheetAY8930[]={
"FreqL_A", "00",
@ -645,7 +645,7 @@ void DivPlatformAY8930::setFlags(unsigned int flags) {
chipClock=COLOR_NTSC/2.0;
break;
}
rate=chipClock/8;
rate=chipClock/4;
for (int i=0; i<3; i++) {
oscBuf[i]->rate=rate;
}

8
src/engine/platform/sound/ay8910.cpp
View File

@ -1064,7 +1064,7 @@ void ay8910_device::sound_stream_update(short** outputs, int outLen)
{
tone = &m_tone[chan];
const int period = std::max<int>(1,tone->period);
tone->count += is_expanded_mode() ? 16 : 1;
tone->count += is_expanded_mode() ? 16 : (m_feature & PSG_HAS_EXPANDED_MODE) ? 2 : 1;
while (tone->count >= period)
{
tone->duty_cycle = (tone->duty_cycle - 1) & 0x1f;
@ -1080,7 +1080,7 @@ void ay8910_device::sound_stream_update(short** outputs, int outLen)
* channels.
*/
m_count_noise = 0;
m_prescale_noise ^= 1;
m_prescale_noise = (m_prescale_noise + 1) & ((m_feature & PSG_HAS_EXPANDED_MODE) ? 3 : 1);
if (!m_prescale_noise || is_expanded_mode()) // AY8930 noise generator rate is twice compares as compatibility mode
{
@ -1469,7 +1469,7 @@ ay8910_device::ay8910_device(device_type type, unsigned int clock,
m_noise_latch(0),
m_mode(0),
m_env_step_mask((!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? 0x0f : 0x1f),
m_step( (!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? 2 : 1),
m_step( (feature & PSG_HAS_EXPANDED_MODE) || (psg_type == PSG_TYPE_AY) ? 2 : 1),
m_zero_is_off( (!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? 1 : 0),
m_par( (!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? &ay8910_param : &ym2149_param),
m_par_env( (!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? &ay8910_param : &ym2149_param_env),
@ -1502,7 +1502,7 @@ void ay8910_device::set_type(psg_type_t psg_type)
else
{
m_env_step_mask = 0x1f;
m_step = 1;
m_step = (m_feature & PSG_HAS_EXPANDED_MODE) ? 2 : 1;
m_zero_is_off = 0;
m_par = &ym2149_param;
m_par_env = &ym2149_param_env;