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c6280.cpp : Fix LFO, Frequency behavior (#4822)

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* c6280.cpp : Fix LFO enable bit

* c6280.cpp : Implement LFO reset bit behavior

* c6280.cpp : Correct frequency behavior, Add notes
This commit is contained in:
cam900 2019-03-30 06:57:45 +09:00 committed by R. Belmont
parent 80a48d5229
commit b9b2a6dd7d
2 changed files with 51 additions and 62 deletions
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104
src/devices/sound/c6280.cpp
View File

@ -92,16 +92,16 @@ void c6280_device::sound_stream_update(sound_stream &stream, stream_sample_t **i
if((ch >= 4) && (m_channel[ch].m_noise_control & 0x80)) if((ch >= 4) && (m_channel[ch].m_noise_control & 0x80))
{ {
/* Noise mode */ /* Noise mode */
uint32_t step = m_noise_freq_tab[(m_channel[ch].m_noise_control & 0x1F) ^ 0x1F]; uint32_t step = (m_channel[ch].m_noise_control & 0x1F) ^ 0x1F;
for (int i = 0; i < samples; i += 1) for (int i = 0; i < samples; i += 1)
{ {
static int data = 0; static int data = 0;
m_channel[ch].m_noise_counter += step; if(m_channel[ch].m_noise_counter <= 0)
if(m_channel[ch].m_noise_counter >= 0x800)
{ {
m_channel[ch].m_noise_counter = step << 2;
data = (machine().rand() & 1) ? 0x1F : 0; data = (machine().rand() & 1) ? 0x1F : 0;
} }
m_channel[ch].m_noise_counter &= 0x7FF; m_channel[ch].m_noise_counter--;
outputs[0][i] += (int16_t)(vll * (data - 16)); outputs[0][i] += (int16_t)(vll * (data - 16));
outputs[1][i] += (int16_t)(vlr * (data - 16)); outputs[1][i] += (int16_t)(vlr * (data - 16));
} }
@ -118,28 +118,40 @@ void c6280_device::sound_stream_update(sound_stream &stream, stream_sample_t **i
} }
else else
{ {
if ((m_lfo_control & 0x80) && (ch < 2)) if ((m_lfo_control & 3) && (ch < 2))
{ {
if (ch == 0) // CH 0 only, CH 1 is muted if (ch == 0) // CH 0 only, CH 1 is muted
{ {
/* Waveform mode with LFO */ /* Waveform mode with LFO */
uint32_t step = m_channel[0].m_frequency; uint16_t lfo_step = m_channel[1].m_frequency ? m_channel[1].m_frequency : 0x1000;
uint16_t lfo_step = m_channel[1].m_frequency;
for (int i = 0; i < samples; i += 1) for (int i = 0; i < samples; i += 1)
{ {
int offset, lfooffset; int32_t step = m_channel[0].m_frequency ? m_channel[0].m_frequency : 0x1000;
int16_t data, lfo_data; if (m_lfo_control & 0x80) // reset LFO
lfooffset = (m_channel[1].m_counter >> 12) & 0x1F; {
m_channel[1].m_counter += m_wave_freq_tab[(lfo_step * m_lfo_frequency) & 0xfff]; // TODO : multiply? verify this from real hardware. m_channel[1].m_tick = lfo_step * m_lfo_frequency;
m_channel[1].m_counter &= 0x1FFFF; m_channel[1].m_counter = 0;
lfo_data = m_channel[1].m_waveform[lfooffset]; }
if (m_lfo_control & 3) else
{
int lfooffset = m_channel[1].m_counter;
m_channel[1].m_tick--;
if (m_channel[1].m_tick <= 0)
{
m_channel[1].m_tick = lfo_step * m_lfo_frequency; // TODO : multiply? verify this from real hardware.
m_channel[1].m_counter = (m_channel[1].m_counter + 1) & 0x1f;
}
int16_t lfo_data = m_channel[1].m_waveform[lfooffset];
step += ((lfo_data - 16) << (((m_lfo_control & 3)-1)<<1)); // verified from patent, TODO : same in real hardware? step += ((lfo_data - 16) << (((m_lfo_control & 3)-1)<<1)); // verified from patent, TODO : same in real hardware?
}
offset = (m_channel[0].m_counter >> 12) & 0x1F; int offset = m_channel[0].m_counter;
m_channel[0].m_counter += m_wave_freq_tab[step & 0xfff]; m_channel[0].m_tick--;
m_channel[0].m_counter &= 0x1FFFF; if (m_channel[0].m_tick <= 0)
data = m_channel[0].m_waveform[offset]; {
m_channel[0].m_tick = step;
m_channel[0].m_counter = (m_channel[0].m_counter + 1) & 0x1f;
}
int16_t data = m_channel[0].m_waveform[offset];
outputs[0][i] += (int16_t)(vll * (data - 16)); outputs[0][i] += (int16_t)(vll * (data - 16));
outputs[1][i] += (int16_t)(vlr * (data - 16)); outputs[1][i] += (int16_t)(vlr * (data - 16));
} }
@ -148,15 +160,17 @@ void c6280_device::sound_stream_update(sound_stream &stream, stream_sample_t **i
else else
{ {
/* Waveform mode */ /* Waveform mode */
uint32_t step = m_wave_freq_tab[m_channel[ch].m_frequency]; uint32_t step = m_channel[ch].m_frequency ? m_channel[ch].m_frequency : 0x1000;
for (int i = 0; i < samples; i += 1) for (int i = 0; i < samples; i += 1)
{ {
int offset; int offset = m_channel[0].m_counter;
int16_t data; m_channel[ch].m_tick--;
offset = (m_channel[ch].m_counter >> 12) & 0x1F; if (m_channel[ch].m_tick <= 0)
m_channel[ch].m_counter += step; {
m_channel[ch].m_counter &= 0x1FFFF; m_channel[ch].m_tick = step;
data = m_channel[ch].m_waveform[offset]; m_channel[ch].m_counter = (m_channel[ch].m_counter + 1) & 0x1f;
}
int16_t data = m_channel[ch].m_waveform[offset];
outputs[0][i] += (int16_t)(vll * (data - 16)); outputs[0][i] += (int16_t)(vll * (data - 16));
outputs[1][i] += (int16_t)(vlr * (data - 16)); outputs[1][i] += (int16_t)(vlr * (data - 16));
} }
@ -205,6 +219,10 @@ WRITE8_MEMBER( c6280_device::c6280_w )
{ {
chan->m_index = 0; chan->m_index = 0;
} }
if(((chan->m_control & 0x80) == 0) && (data & 0x80))
{
chan->m_tick = chan->m_frequency;
}
chan->m_control = data; chan->m_control = data;
break; break;
@ -261,38 +279,9 @@ c6280_device::c6280_device(const machine_config &mconfig, const char *tag, devic
{ {
} }
//-------------------------------------------------
// calculate_clocks - (re)calculate clock-derived
// members
//-------------------------------------------------
void c6280_device::calculate_clocks()
{
int rate = clock() / 16;
/* Make waveform frequency table */
for (int i = 0; i < 4096; i += 1)
{
double step = (16 * 4096) / (i + 1);
m_wave_freq_tab[(1 + i) & 0xFFF] = (uint32_t)step;
}
/* Make noise frequency table */
for (int i = 0; i < 32; i += 1)
{
double step = (16 * 32) / (i+1);
m_noise_freq_tab[i] = (uint32_t)step;
}
if (m_stream != nullptr)
m_stream->set_sample_rate(rate);
else
m_stream = machine().sound().stream_alloc(*this, 0, 2, rate);
}
void c6280_device::device_clock_changed() void c6280_device::device_clock_changed()
{ {
calculate_clocks(); m_stream->set_sample_rate(clock());
} }
//------------------------------------------------- //-------------------------------------------------
@ -311,7 +300,7 @@ void c6280_device::device_start()
m_lfo_control = 0; m_lfo_control = 0;
memset(m_channel, 0, sizeof(channel) * 8); memset(m_channel, 0, sizeof(channel) * 8);
calculate_clocks(); m_stream = machine().sound().stream_alloc(*this, 0, 2, clock());
/* Make volume table */ /* Make volume table */
/* PSG has 48dB volume range spread over 32 steps */ /* PSG has 48dB volume range spread over 32 steps */
@ -338,5 +327,6 @@ void c6280_device::device_start()
save_item(NAME(m_channel[chan].m_noise_control), chan); save_item(NAME(m_channel[chan].m_noise_control), chan);
save_item(NAME(m_channel[chan].m_noise_counter), chan); save_item(NAME(m_channel[chan].m_noise_counter), chan);
save_item(NAME(m_channel[chan].m_counter), chan); save_item(NAME(m_channel[chan].m_counter), chan);
save_item(NAME(m_channel[chan].m_tick), chan);
} }
} }

9
src/devices/sound/c6280.h
View File

@ -8,6 +8,8 @@
class c6280_device : public device_t, public device_sound_interface class c6280_device : public device_t, public device_sound_interface
{ {
public: public:
static constexpr feature_type imperfect_features() { return feature::SOUND; } // Incorrect / Not verified noise / LFO output
c6280_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock); c6280_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
// write only // write only
@ -22,8 +24,6 @@ protected:
virtual void sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples) override; virtual void sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples) override;
private: private:
void calculate_clocks();
struct channel { struct channel {
uint16_t m_frequency; uint16_t m_frequency;
uint8_t m_control; uint8_t m_control;
@ -32,8 +32,9 @@ private:
uint8_t m_index; uint8_t m_index;
int16_t m_dda; int16_t m_dda;
uint8_t m_noise_control; uint8_t m_noise_control;
uint32_t m_noise_counter; int32_t m_noise_counter;
uint32_t m_counter; uint32_t m_counter;
int32_t m_tick;
}; };
// internal state // internal state
@ -44,8 +45,6 @@ private:
uint8_t m_lfo_control; uint8_t m_lfo_control;
channel m_channel[8]; channel m_channel[8];
int16_t m_volume_table[32]; int16_t m_volume_table[32];
uint32_t m_noise_freq_tab[32];
uint32_t m_wave_freq_tab[4096];
}; };
DECLARE_DEVICE_TYPE(C6280, c6280_device) DECLARE_DEVICE_TYPE(C6280, c6280_device)