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c6280.cpp : Fix LFO, Frequency behavior (#4822)
* 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
R. Belmont
parent
80a48d5229
commit
b9b2a6dd7d
@ -92,16 +92,16 @@ void c6280_device::sound_stream_update(sound_stream &stream, stream_sample_t **i
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if((ch >= 4) && (m_channel[ch].m_noise_control & 0x80))
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{
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/* Noise mode */
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uint32_t step = m_noise_freq_tab[(m_channel[ch].m_noise_control & 0x1F) ^ 0x1F];
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uint32_t step = (m_channel[ch].m_noise_control & 0x1F) ^ 0x1F;
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for (int i = 0; i < samples; i += 1)
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{
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static int data = 0;
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m_channel[ch].m_noise_counter += step;
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if(m_channel[ch].m_noise_counter >= 0x800)
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if(m_channel[ch].m_noise_counter <= 0)
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{
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m_channel[ch].m_noise_counter = step << 2;
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data = (machine().rand() & 1) ? 0x1F : 0;
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}
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m_channel[ch].m_noise_counter &= 0x7FF;
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m_channel[ch].m_noise_counter--;
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outputs[0][i] += (int16_t)(vll * (data - 16));
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outputs[1][i] += (int16_t)(vlr * (data - 16));
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}
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@ -118,28 +118,40 @@ void c6280_device::sound_stream_update(sound_stream &stream, stream_sample_t **i
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}
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else
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{
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if ((m_lfo_control & 0x80) && (ch < 2))
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if ((m_lfo_control & 3) && (ch < 2))
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{
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if (ch == 0) // CH 0 only, CH 1 is muted
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{
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/* Waveform mode with LFO */
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uint32_t step = m_channel[0].m_frequency;
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uint16_t lfo_step = m_channel[1].m_frequency;
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uint16_t lfo_step = m_channel[1].m_frequency ? m_channel[1].m_frequency : 0x1000;
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for (int i = 0; i < samples; i += 1)
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{
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int offset, lfooffset;
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int16_t data, lfo_data;
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lfooffset = (m_channel[1].m_counter >> 12) & 0x1F;
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m_channel[1].m_counter += m_wave_freq_tab[(lfo_step * m_lfo_frequency) & 0xfff]; // TODO : multiply? verify this from real hardware.
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m_channel[1].m_counter &= 0x1FFFF;
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lfo_data = m_channel[1].m_waveform[lfooffset];
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if (m_lfo_control & 3)
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int32_t step = m_channel[0].m_frequency ? m_channel[0].m_frequency : 0x1000;
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if (m_lfo_control & 0x80) // reset LFO
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{
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m_channel[1].m_tick = lfo_step * m_lfo_frequency;
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m_channel[1].m_counter = 0;
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}
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else
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{
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int lfooffset = m_channel[1].m_counter;
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m_channel[1].m_tick--;
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if (m_channel[1].m_tick <= 0)
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{
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m_channel[1].m_tick = lfo_step * m_lfo_frequency; // TODO : multiply? verify this from real hardware.
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m_channel[1].m_counter = (m_channel[1].m_counter + 1) & 0x1f;
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}
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int16_t lfo_data = m_channel[1].m_waveform[lfooffset];
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step += ((lfo_data - 16) << (((m_lfo_control & 3)-1)<<1)); // verified from patent, TODO : same in real hardware?
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offset = (m_channel[0].m_counter >> 12) & 0x1F;
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m_channel[0].m_counter += m_wave_freq_tab[step & 0xfff];
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m_channel[0].m_counter &= 0x1FFFF;
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data = m_channel[0].m_waveform[offset];
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}
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int offset = m_channel[0].m_counter;
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m_channel[0].m_tick--;
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if (m_channel[0].m_tick <= 0)
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{
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m_channel[0].m_tick = step;
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m_channel[0].m_counter = (m_channel[0].m_counter + 1) & 0x1f;
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}
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int16_t data = m_channel[0].m_waveform[offset];
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outputs[0][i] += (int16_t)(vll * (data - 16));
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outputs[1][i] += (int16_t)(vlr * (data - 16));
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}
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@ -148,15 +160,17 @@ void c6280_device::sound_stream_update(sound_stream &stream, stream_sample_t **i
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else
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{
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/* Waveform mode */
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uint32_t step = m_wave_freq_tab[m_channel[ch].m_frequency];
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uint32_t step = m_channel[ch].m_frequency ? m_channel[ch].m_frequency : 0x1000;
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for (int i = 0; i < samples; i += 1)
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{
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int offset;
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int16_t data;
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offset = (m_channel[ch].m_counter >> 12) & 0x1F;
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m_channel[ch].m_counter += step;
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m_channel[ch].m_counter &= 0x1FFFF;
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data = m_channel[ch].m_waveform[offset];
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int offset = m_channel[0].m_counter;
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m_channel[ch].m_tick--;
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if (m_channel[ch].m_tick <= 0)
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{
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m_channel[ch].m_tick = step;
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m_channel[ch].m_counter = (m_channel[ch].m_counter + 1) & 0x1f;
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}
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int16_t data = m_channel[ch].m_waveform[offset];
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outputs[0][i] += (int16_t)(vll * (data - 16));
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outputs[1][i] += (int16_t)(vlr * (data - 16));
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}
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@ -205,6 +219,10 @@ WRITE8_MEMBER( c6280_device::c6280_w )
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{
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chan->m_index = 0;
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}
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if(((chan->m_control & 0x80) == 0) && (data & 0x80))
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{
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chan->m_tick = chan->m_frequency;
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}
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chan->m_control = data;
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break;
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@ -261,38 +279,9 @@ c6280_device::c6280_device(const machine_config &mconfig, const char *tag, devic
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{
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}
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//-------------------------------------------------
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// calculate_clocks - (re)calculate clock-derived
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// members
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//-------------------------------------------------
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void c6280_device::calculate_clocks()
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{
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int rate = clock() / 16;
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/* Make waveform frequency table */
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for (int i = 0; i < 4096; i += 1)
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{
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double step = (16 * 4096) / (i + 1);
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m_wave_freq_tab[(1 + i) & 0xFFF] = (uint32_t)step;
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}
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/* Make noise frequency table */
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for (int i = 0; i < 32; i += 1)
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{
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double step = (16 * 32) / (i+1);
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m_noise_freq_tab[i] = (uint32_t)step;
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}
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if (m_stream != nullptr)
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m_stream->set_sample_rate(rate);
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else
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m_stream = machine().sound().stream_alloc(*this, 0, 2, rate);
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}
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void c6280_device::device_clock_changed()
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{
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calculate_clocks();
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m_stream->set_sample_rate(clock());
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}
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//-------------------------------------------------
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@ -311,7 +300,7 @@ void c6280_device::device_start()
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m_lfo_control = 0;
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memset(m_channel, 0, sizeof(channel) * 8);
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calculate_clocks();
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m_stream = machine().sound().stream_alloc(*this, 0, 2, clock());
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/* Make volume table */
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/* PSG has 48dB volume range spread over 32 steps */
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@ -338,5 +327,6 @@ void c6280_device::device_start()
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save_item(NAME(m_channel[chan].m_noise_control), chan);
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save_item(NAME(m_channel[chan].m_noise_counter), chan);
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save_item(NAME(m_channel[chan].m_counter), chan);
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save_item(NAME(m_channel[chan].m_tick), chan);
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}
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}
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@ -8,6 +8,8 @@
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class c6280_device : public device_t, public device_sound_interface
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{
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public:
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static constexpr feature_type imperfect_features() { return feature::SOUND; } // Incorrect / Not verified noise / LFO output
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c6280_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
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// write only
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@ -22,8 +24,6 @@ protected:
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virtual void sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples) override;
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private:
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void calculate_clocks();
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struct channel {
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uint16_t m_frequency;
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uint8_t m_control;
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@ -32,8 +32,9 @@ private:
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uint8_t m_index;
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int16_t m_dda;
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uint8_t m_noise_control;
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uint32_t m_noise_counter;
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int32_t m_noise_counter;
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uint32_t m_counter;
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int32_t m_tick;
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};
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// internal state
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@ -44,8 +45,6 @@ private:
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uint8_t m_lfo_control;
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channel m_channel[8];
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int16_t m_volume_table[32];
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uint32_t m_noise_freq_tab[32];
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uint32_t m_wave_freq_tab[4096];
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};
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DECLARE_DEVICE_TYPE(C6280, c6280_device)
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