mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
synced 2024-12-29 20:51:49 +01:00
cc056b92db
Initial test that indicated power-on latched register was noise attenuation register was flawed because it wasn't done after a "cold" power-on. It appears the latched value is not totally reseted when doing a quick power off/on cycle (which was done with initial test) and would keep last value being set.
604 lines
17 KiB
C
604 lines
17 KiB
C
/***************************************************************************************
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* Genesis Plus
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* PSG sound chip (SN76489A compatible)
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*
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* Support for discrete chip & integrated (ASIC) clones
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*
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* Noise implementation based on http://www.smspower.org/Development/SN76489#NoiseChannel
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*
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* Copyright (C) 2016-2017 Eke-Eke (Genesis Plus GX)
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*
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* Redistribution and use of this code or any derivative works are permitted
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* provided that the following conditions are met:
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*
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* - Redistributions may not be sold, nor may they be used in a commercial
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* product or activity.
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*
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* - Redistributions that are modified from the original source must include the
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* complete source code, including the source code for all components used by a
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* binary built from the modified sources. However, as a special exception, the
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* source code distributed need not include anything that is normally distributed
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* (in either source or binary form) with the major components (compiler, kernel,
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* and so on) of the operating system on which the executable runs, unless that
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* component itself accompanies the executable.
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*
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* - Redistributions must reproduce the above copyright notice, this list of
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* conditions and the following disclaimer in the documentation and/or other
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* materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************************/
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#include "shared.h"
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#include "blip_buf.h"
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/* internal clock = input clock : 16 = (master clock : 15) : 16 */
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#define PSG_MCYCLES_RATIO (15*16)
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/* maximal channel output (roughly adjusted to match VA4 MD1 PSG/FM balance with 1.5x amplification of PSG output) */
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#define PSG_MAX_VOLUME 2800
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static const uint8 noiseShiftWidth[2] = {14,15};
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static const uint8 noiseBitMask[2] = {0x6,0x9};
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static const uint8 noiseFeedback[10] = {0,1,1,0,1,0,0,1,1,0};
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static const uint16 chanVolume[16] = {
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PSG_MAX_VOLUME, /* MAX */
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PSG_MAX_VOLUME * 0.794328234, /* -2dB */
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PSG_MAX_VOLUME * 0.630957344, /* -4dB */
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PSG_MAX_VOLUME * 0.501187233, /* -6dB */
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PSG_MAX_VOLUME * 0.398107170, /* -8dB */
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PSG_MAX_VOLUME * 0.316227766, /* -10dB */
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PSG_MAX_VOLUME * 0.251188643, /* -12dB */
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PSG_MAX_VOLUME * 0.199526231, /* -14dB */
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PSG_MAX_VOLUME * 0.158489319, /* -16dB */
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PSG_MAX_VOLUME * 0.125892541, /* -18dB */
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PSG_MAX_VOLUME * 0.1, /* -20dB */
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PSG_MAX_VOLUME * 0.079432823, /* -22dB */
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PSG_MAX_VOLUME * 0.063095734, /* -24dB */
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PSG_MAX_VOLUME * 0.050118723, /* -26dB */
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PSG_MAX_VOLUME * 0.039810717, /* -28dB */
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0 /* OFF */
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};
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static struct
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{
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int clocks;
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int latch;
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int zeroFreqInc;
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int noiseShiftValue;
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int noiseShiftWidth;
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int noiseBitMask;
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int regs[8];
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int freqInc[4];
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int freqCounter[4];
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int polarity[4];
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int chanDelta[4][2];
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int chanOut[4][2];
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int chanAmp[4][2];
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} psg;
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static void psg_update(unsigned int clocks);
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void psg_init(PSG_TYPE type)
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{
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int i;
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/* Initialize stereo amplification (default) */
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for (i=0; i<4; i++)
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{
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psg.chanAmp[i][0] = 100;
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psg.chanAmp[i][1] = 100;
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}
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/* Initialize Tone zero frequency increment value */
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psg.zeroFreqInc = ((type == PSG_DISCRETE) ? 0x400 : 0x1) * PSG_MCYCLES_RATIO;
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/* Initialize Noise LSFR type */
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psg.noiseShiftWidth = noiseShiftWidth[type];
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psg.noiseBitMask = noiseBitMask[type];
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}
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void psg_reset()
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{
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int i;
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/* power-on state (verified on 315-5313A & 315-5660 integrated version only) */
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for (i=0; i<4; i++)
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{
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psg.regs[i*2] = 0;
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psg.regs[i*2+1] = 0;
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psg.freqInc[i] = (i < 3) ? (psg.zeroFreqInc) : (16 * PSG_MCYCLES_RATIO);
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psg.freqCounter[i] = 0;
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psg.polarity[i] = -1;
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psg.chanDelta[i][0] = 0;
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psg.chanDelta[i][1] = 0;
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psg.chanOut[i][0] = 0;
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psg.chanOut[i][1] = 0;
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}
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/* tone #2 attenuation register is latched on power-on (verified on 315-5313A integrated version only) */
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psg.latch = 3;
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/* reset noise shift register */
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psg.noiseShiftValue = 1 << psg.noiseShiftWidth;
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/* reset internal M-cycles clock counter */
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psg.clocks = 0;
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}
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int psg_context_save(uint8 *state)
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{
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int bufferptr = 0;
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save_param(&psg.clocks,sizeof(psg.clocks));
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save_param(&psg.latch,sizeof(psg.latch));
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save_param(&psg.noiseShiftValue,sizeof(psg.noiseShiftValue));
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save_param(psg.regs,sizeof(psg.regs));
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save_param(psg.freqInc,sizeof(psg.freqInc));
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save_param(psg.freqCounter,sizeof(psg.freqCounter));
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save_param(psg.polarity,sizeof(psg.polarity));
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save_param(psg.chanDelta,sizeof(psg.chanDelta));
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save_param(psg.chanOut,sizeof(psg.chanOut));
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return bufferptr;
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}
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int psg_context_load(uint8 *state)
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{
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int chanOut[4][2], delta[2];
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int i, bufferptr = 0;
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/* get current tone channels output */
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for (i=0; i<3; i++)
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{
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if (psg.polarity[i] > 0)
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{
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chanOut[i][0] = psg.chanOut[i][0];
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chanOut[i][1] = psg.chanOut[i][1];
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}
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else
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{
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chanOut[i][0] = 0;
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chanOut[i][1] = 0;
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}
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}
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/* get current noise channel output */
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if (psg.noiseShiftValue & 1)
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{
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chanOut[3][0] = psg.chanOut[3][0];
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chanOut[3][1] = psg.chanOut[3][1];
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}
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else
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{
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chanOut[3][0] = 0;
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chanOut[3][1] = 0;
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}
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load_param(&psg.clocks,sizeof(psg.clocks));
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load_param(&psg.latch,sizeof(psg.latch));
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load_param(&psg.noiseShiftValue,sizeof(psg.noiseShiftValue));
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load_param(psg.regs,sizeof(psg.regs));
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load_param(psg.freqInc,sizeof(psg.freqInc));
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load_param(psg.freqCounter,sizeof(psg.freqCounter));
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load_param(psg.polarity,sizeof(psg.polarity));
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load_param(psg.chanDelta,sizeof(psg.chanDelta));
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load_param(psg.chanOut,sizeof(psg.chanOut));
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/* apply any pending channel volume variation */
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for (i=0; i<4; i++)
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{
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psg.chanOut[i][0] += psg.chanDelta[i][0];
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psg.chanOut[i][1] += psg.chanDelta[i][1];
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psg.chanDelta[i][0] = 0;
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psg.chanDelta[i][1] = 0;
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}
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/* calculate noise channel output variations */
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if (psg.noiseShiftValue & 1)
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{
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/* channel output is high */
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delta[0] = psg.chanOut[3][0] - chanOut[3][0];
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delta[1] = psg.chanOut[3][0] - chanOut[3][1];
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}
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else
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{
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/* channel output is low */
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delta[0] = -chanOut[3][0];
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delta[1] = -chanOut[3][1];
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}
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/* add tone channels output variations */
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for (i=0; i<3; i++)
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{
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if (psg.polarity[i] > 0)
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{
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/* channel output is high */
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delta[0] += (psg.chanOut[i][0] - chanOut[i][0]);
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delta[1] += (psg.chanOut[i][0] - chanOut[i][1]);
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}
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else
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{
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/* channel output is low */
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delta[0] -= chanOut[i][0];
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delta[1] -= chanOut[i][1];
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}
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}
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/* update mixed channels output */
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if (config.hq_psg)
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{
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blip_add_delta(snd.blips[0], psg.clocks, delta[0], delta[1]);
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}
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else
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{
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blip_add_delta_fast(snd.blips[0], psg.clocks, delta[0], delta[1]);
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}
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return bufferptr;
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}
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void psg_write(unsigned int clocks, unsigned int data)
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{
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int index;
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/* PSG chip synchronization */
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if (clocks > psg.clocks)
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{
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/* run PSG chip until current timestamp */
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psg_update(clocks);
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/* update internal M-cycles clock counter */
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psg.clocks += ((clocks - psg.clocks + PSG_MCYCLES_RATIO - 1) / PSG_MCYCLES_RATIO) * PSG_MCYCLES_RATIO;
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}
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if (data & 0x80)
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{
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/* latch register index (1xxx----) */
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psg.latch = index = (data >> 4) & 0x07;
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}
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else
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{
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/* restore latched register index */
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index= psg.latch;
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}
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switch (index)
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{
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case 0:
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case 2:
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case 4: /* Tone channels frequency */
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{
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/* recalculate frequency register value */
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if (data & 0x80)
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{
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/* update 10-bit register LSB (1---xxxx) */
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data = (psg.regs[index] & 0x3f0) | (data & 0x0f);
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}
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else
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{
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/* update 10-bit register MSB (0-xxxxxx) */
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data = (psg.regs[index] & 0x00f) | ((data & 0x3f) << 4);
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}
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/* update channel M-cycle counter increment */
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if (data)
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{
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psg.freqInc[index>>1] = data * PSG_MCYCLES_RATIO;
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}
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else
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{
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/* zero value behaves the same as a value of 1 on integrated version (0x400 on discrete version) */
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psg.freqInc[index>>1] = psg.zeroFreqInc;
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}
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/* update noise channel counter increment if required */
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if ((index == 4) && ((psg.regs[6] & 0x03) == 0x03))
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{
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psg.freqInc[3] = psg.freqInc[2];
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}
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break;
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}
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case 6: /* Noise control */
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{
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/* noise signal generator frequency (----?xxx) */
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int noiseFreq = (data & 0x03);
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if (noiseFreq == 0x03)
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{
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/* noise generator is controlled by tone channel #3 generator */
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psg.freqInc[3] = psg.freqInc[2];
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psg.freqCounter[3] = psg.freqCounter[2];
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}
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else
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{
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/* noise generator is running at separate frequency */
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psg.freqInc[3] = (0x10 << noiseFreq) * PSG_MCYCLES_RATIO;
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}
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/* check current noise shift register output */
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if (psg.noiseShiftValue & 1)
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{
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/* high to low transition will be applied at next internal cycle update */
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psg.chanDelta[3][0] = -psg.chanOut[3][0];
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psg.chanDelta[3][1] = -psg.chanOut[3][1];
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}
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/* reset noise shift register value (noise channel output is forced low) */
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psg.noiseShiftValue = 1 << psg.noiseShiftWidth;;
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break;
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}
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case 7: /* Noise channel attenuation */
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{
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/* convert 4-bit attenuation value (----xxxx) to 16-bit volume value */
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data = chanVolume[data & 0x0f];
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/* check noise shift register output */
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if (psg.noiseShiftValue & 1)
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{
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/* channel output is high, volume variation will be applied at next internal cycle update */
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psg.chanDelta[3][0] = ((data * psg.chanAmp[3][0]) / 100) - psg.chanOut[3][0];
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psg.chanDelta[3][1] = ((data * psg.chanAmp[3][1]) / 100) - psg.chanOut[3][1];
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}
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else
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{
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/* channel output is low, volume variation will be applied at next transition */
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psg.chanOut[3][0] = (data * psg.chanAmp[3][0]) / 100;
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psg.chanOut[3][1] = (data * psg.chanAmp[3][1]) / 100;
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}
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break;
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}
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default: /* Tone channels attenuation */
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{
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/* channel number (0-2) */
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int i = index >> 1;
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/* convert 4-bit attenuation value (----xxxx) to 16-bit volume value */
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data = chanVolume[data & 0x0f];
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/* check tone generator polarity */
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if (psg.polarity[i] > 0)
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{
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/* channel output is high, volume variation will be applied at next internal cycle update */
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psg.chanDelta[i][0] = ((data * psg.chanAmp[i][0]) / 100) - psg.chanOut[i][0];
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psg.chanDelta[i][1] = ((data * psg.chanAmp[i][1]) / 100) - psg.chanOut[i][1];
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}
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else
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{
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/* channel output is low, volume variation will be applied at next transition */
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psg.chanOut[i][0] = (data * psg.chanAmp[i][0]) / 100;
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psg.chanOut[i][1] = (data * psg.chanAmp[i][1]) / 100;
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}
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break;
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}
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}
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/* save register value */
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psg.regs[index] = data;
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}
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void psg_config(unsigned int clocks, unsigned int preamp, unsigned int panning)
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{
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int i;
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/* PSG chip synchronization */
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if (clocks > psg.clocks)
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{
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/* run PSG chip until current timestamp */
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psg_update(clocks);
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/* update internal M-cycles clock counter */
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psg.clocks += ((clocks - psg.clocks + PSG_MCYCLES_RATIO - 1) / PSG_MCYCLES_RATIO) * PSG_MCYCLES_RATIO;
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}
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for (i=0; i<4; i++)
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{
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/* channel internal volume */
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int volume = psg.regs[i*2+1];
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/* update channel stereo amplification */
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psg.chanAmp[i][0] = preamp * ((panning >> (i + 4)) & 1);
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psg.chanAmp[i][1] = preamp * ((panning >> (i + 0)) & 1);
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/* tone channels */
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if (i < 3)
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{
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/* check tone generator polarity */
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if (psg.polarity[i] > 0)
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{
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/* channel output is high, volume variation will be applied at next internal cycle update */
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psg.chanDelta[i][0] = ((volume * psg.chanAmp[i][0]) / 100) - psg.chanOut[i][0];
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psg.chanDelta[i][1] = ((volume * psg.chanAmp[i][1]) / 100) - psg.chanOut[i][1];
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}
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else
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{
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/* channel output is low, volume variation will be applied at next transition*/
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psg.chanOut[i][0] = (volume * psg.chanAmp[i][0]) / 100;
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psg.chanOut[i][1] = (volume * psg.chanAmp[i][1]) / 100;
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}
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}
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/* noise channel */
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else
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{
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/* check noise shift register output */
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if (psg.noiseShiftValue & 1)
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{
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/* channel output is high, volume variation will be applied at next internal cycle update */
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psg.chanDelta[3][0] = ((volume * psg.chanAmp[3][0]) / 100) - psg.chanOut[3][0];
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psg.chanDelta[3][1] = ((volume * psg.chanAmp[3][1]) / 100) - psg.chanOut[3][1];
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}
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else
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{
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/* channel output is low, volume variation will be applied at next transition */
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psg.chanOut[3][0] = (volume * psg.chanAmp[3][0]) / 100;
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psg.chanOut[3][1] = (volume * psg.chanAmp[3][1]) / 100;
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}
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}
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}
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}
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void psg_end_frame(unsigned int clocks)
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{
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int i;
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if (clocks > psg.clocks)
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{
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/* run PSG chip until current timestamp */
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psg_update(clocks);
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/* update internal M-cycles clock counter */
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psg.clocks += ((clocks - psg.clocks + PSG_MCYCLES_RATIO - 1) / PSG_MCYCLES_RATIO) * PSG_MCYCLES_RATIO;
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}
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/* adjust internal M-cycles clock counter for next frame */
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psg.clocks -= clocks;
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/* adjust channels time counters for next frame */
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for (i=0; i<4; ++i)
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{
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|
psg.freqCounter[i] -= clocks;
|
|
}
|
|
}
|
|
|
|
static void psg_update(unsigned int clocks)
|
|
{
|
|
int i, timestamp, polarity;
|
|
|
|
for (i=0; i<4; i++)
|
|
{
|
|
/* apply any pending channel volume variations */
|
|
if (psg.chanDelta[i][0] | psg.chanDelta[i][1])
|
|
{
|
|
/* update channel output */
|
|
if (config.hq_psg)
|
|
{
|
|
blip_add_delta(snd.blips[0], psg.clocks, psg.chanDelta[i][0], psg.chanDelta[i][1]);
|
|
}
|
|
else
|
|
{
|
|
blip_add_delta_fast(snd.blips[0], psg.clocks, psg.chanDelta[i][0], psg.chanDelta[i][1]);
|
|
}
|
|
|
|
/* update channel volume */
|
|
psg.chanOut[i][0] += psg.chanDelta[i][0];
|
|
psg.chanOut[i][1] += psg.chanDelta[i][1];
|
|
|
|
/* clear pending channel volume variations */
|
|
psg.chanDelta[i][0] = 0;
|
|
psg.chanDelta[i][1] = 0;
|
|
}
|
|
|
|
/* timestamp of next transition */
|
|
timestamp = psg.freqCounter[i];
|
|
|
|
/* current channel generator polarity */
|
|
polarity = psg.polarity[i];
|
|
|
|
/* Tone channels */
|
|
if (i < 3)
|
|
{
|
|
/* process all transitions occurring until current clock timestamp */
|
|
while (timestamp < clocks)
|
|
{
|
|
/* invert tone generator polarity */
|
|
polarity = -polarity;
|
|
|
|
/* update channel output */
|
|
if (config.hq_psg)
|
|
{
|
|
blip_add_delta(snd.blips[0], timestamp, polarity*psg.chanOut[i][0], polarity*psg.chanOut[i][1]);
|
|
}
|
|
else
|
|
{
|
|
blip_add_delta_fast(snd.blips[0], timestamp, polarity*psg.chanOut[i][0], polarity*psg.chanOut[i][1]);
|
|
}
|
|
|
|
/* timestamp of next transition */
|
|
timestamp += psg.freqInc[i];
|
|
}
|
|
}
|
|
|
|
/* Noise channel */
|
|
else
|
|
{
|
|
/* current noise shift register value */
|
|
int shiftValue = psg.noiseShiftValue;
|
|
|
|
/* process all transitions occurring until current clock timestamp */
|
|
while (timestamp < clocks)
|
|
{
|
|
/* invert noise generator polarity */
|
|
polarity = -polarity;
|
|
|
|
/* noise register is shifted on positive edge only */
|
|
if (polarity > 0)
|
|
{
|
|
/* current shift register output */
|
|
int shiftOutput = shiftValue & 0x01;
|
|
|
|
/* White noise (----1xxx) */
|
|
if (psg.regs[6] & 0x04)
|
|
{
|
|
/* shift and apply XOR feedback network */
|
|
shiftValue = (shiftValue >> 1) | (noiseFeedback[shiftValue & psg.noiseBitMask] << psg.noiseShiftWidth);
|
|
}
|
|
|
|
/* Periodic noise (----0xxx) */
|
|
else
|
|
{
|
|
/* shift and feedback current output */
|
|
shiftValue = (shiftValue >> 1) | (shiftOutput << psg.noiseShiftWidth);
|
|
}
|
|
|
|
/* shift register output variation */
|
|
shiftOutput = (shiftValue & 0x1) - shiftOutput;
|
|
|
|
/* update noise channel output */
|
|
if (config.hq_psg)
|
|
{
|
|
blip_add_delta(snd.blips[0], timestamp, shiftOutput*psg.chanOut[3][0], shiftOutput*psg.chanOut[3][1]);
|
|
}
|
|
else
|
|
{
|
|
blip_add_delta_fast(snd.blips[0], timestamp, shiftOutput*psg.chanOut[3][0], shiftOutput*psg.chanOut[3][1]);
|
|
}
|
|
}
|
|
|
|
/* timestamp of next transition */
|
|
timestamp += psg.freqInc[3];
|
|
}
|
|
|
|
/* save shift register value */
|
|
psg.noiseShiftValue = shiftValue;
|
|
}
|
|
|
|
/* save timestamp of next transition */
|
|
psg.freqCounter[i] = timestamp;
|
|
|
|
/* save channel generator polarity */
|
|
psg.polarity[i] = polarity;
|
|
}
|
|
}
|