libsidplayfp  2.3.1
WaveformGenerator.h
1 /*
2  * This file is part of libsidplayfp, a SID player engine.
3  *
4  * Copyright 2011-2016 Leandro Nini <drfiemost@users.sourceforge.net>
5  * Copyright 2007-2010 Antti Lankila
6  * Copyright 2004,2010 Dag Lem <resid@nimrod.no>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License as published by
10  * the Free Software Foundation; either version 2 of the License, or
11  * (at your option) any later version.
12  *
13  * This program is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16  * GNU General Public License for more details.
17  *
18  * You should have received a copy of the GNU General Public License
19  * along with this program; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
21  */
22 
23 #ifndef WAVEFORMGENERATOR_H
24 #define WAVEFORMGENERATOR_H
25 
26 #include "siddefs-fp.h"
27 #include "array.h"
28 
29 #include "sidcxx11.h"
30 
31 namespace reSIDfp
32 {
33 
87 {
88 private:
89  matrix_t* model_wave;
90 
91  short* wave;
92 
93  // PWout = (PWn/40.95)%
94  unsigned int pw;
95 
96  unsigned int shift_register;
97 
99  int shift_pipeline;
100 
101  unsigned int ring_msb_mask;
102  unsigned int no_noise;
103  unsigned int noise_output;
104  unsigned int no_noise_or_noise_output;
105  unsigned int no_pulse;
106  unsigned int pulse_output;
107 
109  unsigned int waveform;
110 
111  unsigned int waveform_output;
112 
114  unsigned int accumulator;
115 
116  // Fout = (Fn*Fclk/16777216)Hz
117  unsigned int freq;
118 
120  unsigned int tri_saw_pipeline;
121 
123  unsigned int osc3;
124 
126  unsigned int shift_register_reset;
127 
128  // The wave signal TTL when no waveform is selected
129  unsigned int floating_output_ttl;
130 
132 
133  bool test;
134  bool sync;
136 
138  bool msb_rising;
139 
140  bool is6581; //-V730_NOINIT this is initialized in the SID constructor
141 
143  float* dac; //-V730_NOINIT this is initialized in the SID constructor
144 
145 private:
146  void clock_shift_register(unsigned int bit0);
147 
148  unsigned int get_noise_writeback();
149 
150  void write_shift_register();
151 
152  void set_noise_output();
153 
154  void set_no_noise_or_noise_output();
155 
156  void waveBitfade();
157 
158  void shiftregBitfade();
159 
160 public:
161  void setWaveformModels(matrix_t* models);
162 
170  void setDAC(float* dac) { this->dac = dac; }
171 
178  void setModel(bool is6581) { this->is6581 = is6581; }
179 
183  void clock();
184 
193  void synchronize(WaveformGenerator* syncDest, const WaveformGenerator* syncSource) const;
194 
199  model_wave(nullptr),
200  wave(nullptr),
201  pw(0),
202  shift_register(0),
203  shift_pipeline(0),
204  ring_msb_mask(0),
205  no_noise(0),
206  noise_output(0),
207  no_noise_or_noise_output(0),
208  no_pulse(0),
209  pulse_output(0),
210  waveform(0),
211  waveform_output(0),
212  accumulator(0x555555), // Accumulator's even bits are high on powerup
213  freq(0),
214  tri_saw_pipeline(0x555),
215  osc3(0),
216  shift_register_reset(0),
217  floating_output_ttl(0),
218  test(false),
219  sync(false),
220  msb_rising(false) {}
221 
227  void writeFREQ_LO(unsigned char freq_lo) { freq = (freq & 0xff00) | (freq_lo & 0xff); }
228 
234  void writeFREQ_HI(unsigned char freq_hi) { freq = (freq_hi << 8 & 0xff00) | (freq & 0xff); }
235 
241  void writePW_LO(unsigned char pw_lo) { pw = (pw & 0xf00) | (pw_lo & 0x0ff); }
242 
248  void writePW_HI(unsigned char pw_hi) { pw = (pw_hi << 8 & 0xf00) | (pw & 0x0ff); }
249 
255  void writeCONTROL_REG(unsigned char control);
256 
260  void reset();
261 
268  float output(const WaveformGenerator* ringModulator);
269 
273  unsigned char readOSC() const { return static_cast<unsigned char>(osc3 >> 4); }
274 
278  unsigned int readAccumulator() const { return accumulator; }
279 
283  unsigned int readFreq() const { return freq; }
284 
288  bool readTest() const { return test; }
289 
293  bool readSync() const { return sync; }
294 };
295 
296 } // namespace reSIDfp
297 
298 #if RESID_INLINING || defined(WAVEFORMGENERATOR_CPP)
299 
300 namespace reSIDfp
301 {
302 
303 RESID_INLINE
305 {
306  if (unlikely(test))
307  {
308  if (unlikely(shift_register_reset != 0) && unlikely(--shift_register_reset == 0))
309  {
310  shiftregBitfade();
311 
312  // New noise waveform output.
313  set_noise_output();
314  }
315 
316  // The test bit sets pulse high.
317  pulse_output = 0xfff;
318  }
319  else
320  {
321  // Calculate new accumulator value;
322  const unsigned int accumulator_old = accumulator;
323  accumulator = (accumulator + freq) & 0xffffff;
324 
325  // Check which bit have changed
326  const unsigned int accumulator_bits_set = ~accumulator_old & accumulator;
327 
328  // Check whether the MSB is set high. This is used for synchronization.
329  msb_rising = (accumulator_bits_set & 0x800000) != 0;
330 
331  // Shift noise register once for each time accumulator bit 19 is set high.
332  // The shift is delayed 2 cycles.
333  if (unlikely((accumulator_bits_set & 0x080000) != 0))
334  {
335  // Pipeline: Detect rising bit, shift phase 1, shift phase 2.
336  shift_pipeline = 2;
337  }
338  else if (unlikely(shift_pipeline != 0) && --shift_pipeline == 0)
339  {
340  // bit0 = (bit22 | test) ^ bit17
341  clock_shift_register(((shift_register << 22) ^ (shift_register << 17)) & (1 << 22));
342  }
343  }
344 }
345 
346 RESID_INLINE
347 float WaveformGenerator::output(const WaveformGenerator* ringModulator)
348 {
349  // Set output value.
350  if (likely(waveform != 0))
351  {
352  const unsigned int ix = (accumulator ^ (~ringModulator->accumulator & ring_msb_mask)) >> 12;
353 
354  // The bit masks no_pulse and no_noise are used to achieve branch-free
355  // calculation of the output value.
356  waveform_output = wave[ix] & (no_pulse | pulse_output) & no_noise_or_noise_output;
357 
358  // Triangle/Sawtooth output is delayed half cycle on 8580.
359  // This will appear as a one cycle delay on OSC3 as it is latched first phase of the clock.
360  if ((waveform & 3) && !is6581)
361  {
362  osc3 = tri_saw_pipeline & (no_pulse | pulse_output) & no_noise_or_noise_output;
363  tri_saw_pipeline = wave[ix];
364  }
365  else
366  {
367  osc3 = waveform_output;
368  }
369 
370  // In the 6581 the top bit of the accumulator may be driven low by combined waveforms
371  // when the sawtooth is selected
372  // FIXME doesn't seem to always happen
373  if ((waveform & 2) && unlikely(waveform & 0xd) && is6581)
374  accumulator &= (waveform_output << 12) | 0x7fffff;
375 
376  write_shift_register();
377  }
378  else
379  {
380  // Age floating DAC input.
381  if (likely(floating_output_ttl != 0) && unlikely(--floating_output_ttl == 0))
382  {
383  waveBitfade();
384  }
385  }
386 
387  // The pulse level is defined as (accumulator >> 12) >= pw ? 0xfff : 0x000.
388  // The expression -((accumulator >> 12) >= pw) & 0xfff yields the same
389  // results without any branching (and thus without any pipeline stalls).
390  // NB! This expression relies on that the result of a boolean expression
391  // is either 0 or 1, and furthermore requires two's complement integer.
392  // A few more cycles may be saved by storing the pulse width left shifted
393  // 12 bits, and dropping the and with 0xfff (this is valid since pulse is
394  // used as a bit mask on 12 bit values), yielding the expression
395  // -(accumulator >= pw24). However this only results in negligible savings.
396 
397  // The result of the pulse width compare is delayed one cycle.
398  // Push next pulse level into pulse level pipeline.
399  pulse_output = ((accumulator >> 12) >= pw) ? 0xfff : 0x000;
400 
401  // DAC imperfections are emulated by using waveform_output as an index
402  // into a DAC lookup table. readOSC() uses waveform_output directly.
403  return dac[waveform_output];
404 }
405 
406 } // namespace reSIDfp
407 
408 #endif
409 
410 #endif
Definition: array.h:43
Definition: WaveformGenerator.h:87
void synchronize(WaveformGenerator *syncDest, const WaveformGenerator *syncSource) const
Definition: WaveformGenerator.cpp:173
bool readTest() const
Definition: WaveformGenerator.h:288
void clock()
Definition: WaveformGenerator.h:304
unsigned int readFreq() const
Definition: WaveformGenerator.h:283
void writePW_HI(unsigned char pw_hi)
Definition: WaveformGenerator.h:248
void writeFREQ_HI(unsigned char freq_hi)
Definition: WaveformGenerator.h:234
void writePW_LO(unsigned char pw_lo)
Definition: WaveformGenerator.h:241
unsigned char readOSC() const
Definition: WaveformGenerator.h:273
void writeFREQ_LO(unsigned char freq_lo)
Definition: WaveformGenerator.h:227
void writeCONTROL_REG(unsigned char control)
Definition: WaveformGenerator.cpp:243
WaveformGenerator()
Definition: WaveformGenerator.h:198
unsigned int readAccumulator() const
Definition: WaveformGenerator.h:278
void setDAC(float *dac)
Definition: WaveformGenerator.h:170
bool readSync() const
Definition: WaveformGenerator.h:293
void setModel(bool is6581)
Definition: WaveformGenerator.h:178
void reset()
Definition: WaveformGenerator.cpp:323
float output(const WaveformGenerator *ringModulator)
Definition: WaveformGenerator.h:347