sid.h

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/*
 * This source is a modifed version of sidengine.c from here: https://github.com/wothke/websid
 * Modification is mainly about killing the not-SID related parts, and making emulation modular,
 * ie introducing a way to allow to emulate more SIDs through the SidEmulation structure pointer.
 * Otherwise it should be the same. Sorry, I am just lame with sound things, the modularization
 * can be done in a better way, ie some things should not be per SID stuff, etc.
 * Modifications done by: Gabor Lenart (aka LGB) lgblgblgb@gmail.com http://lgb.hu/
 * Mainly for having *some* sound for my primitive Commodore 65 emulator :)
 * https://github.com/lgblgblgb/xclcd
 *
 * ---- NOW THE ORIGINAL COMMENT HEADER FOLLOWS ----
 *
 * This file is largely the original file from the "TinySid for Linux" distribution.
 *
 * <p>TinySid (c) 1999-2012 T. Hinrichs, R. Sinsch
 *
 * <p>It was updated by merging in the latest "Rockbox" version (This noticably fixed playback problems with
 * "Yie Ar Kung Fu"..) and by applying fixes contributed by Markus Gritsch. Unfortunately a revision history of the old
 * TinySid codebase does not seem to exist.. so we'll probably never know what was used for the TinySid Windows executable and
 * why it is the only version that correctly plays Electric_Girls.sid..)
 * <p>In this file I deliberately kept the "naming conventions" used in the original TinySID code - to ease future merging
 * of potential TinySid fixes (consequently there is a mismatch with the conventions that I am using in my own code..)
 *
 * <p>My additions here are:
 *   <ol>
 *    <li>fixed PSID digi playback volume (was originally too low)
 *    <li>correct cycle-time calculation for ALL 6510 op codes (also illegal ones)
 *    <li>added impls for illegal 6510 op codes, fixed errors in V-flag calculation, added handling for 6510 addressing "bugs"
 *    <li>poor man's VIC and CIA handling
 *    <li>"cycle limit" feature used to interrupt emulation runs (e.g. main prog can now be suspended/continued)
 *    <li>Poor man's "combined pulse/triangle waveform" impl to allow playback of songs like Kentilla.sid.
 *    <li>added RSID digi playback support (D418 based as well as "pulse width modulation" based): it is a "special feature" of
 *    this implementation that regular SID emulation is performed somewhat independently from the handling of digi samples, i.e. playback
 *    of digi samples is tracked separately (for main, IRQ and NMI) and the respective digi samples are then merged with the regular SID
 *    output as some kind of postprocessing step
 *    <li> replaced original "envelope generator" impl with a more realistic one (incl. "ADSR-bug" handling)
 *  </ol>
 *
 *      FIXME: refactor CPU and SID emulation into separate files..
 *
 * known limitation: basic-ROM specific handling not implemented...
 *
 * <p>Notice: if you have questions regarding the details of the below SID emulation, then you should better get in touch with R.Sinsch :-)
 *
 * <p>Tiny'R'Sid add-ons (c) 2015 J.Wothke
 *
 * Terms of Use: This software is licensed under a CC BY-NC-SA
 * (http://creativecommons.org/licenses/by-nc-sa/4.0/).
 */
 
#ifndef __SIDENGINE_H_IS_INCLUDED
#define __SIDENGINE_H_IS_INCLUDED
 
#include <SDL_atomic.h>
 
// 0x38: supposedly DC level for MOS6581 (whereas it would be 0x80 for the "crappy new chip")
#define SID_DC_LEVEL 0x38
 
#define SID_USES_FILTER
//#define SID_DEBUG
 
// switch between 'cycle' or 'sample' based envelope-generator counter
// (performance wise it does not seem to make much difference)
//#define SID_USES_SAMPLE_ENV_COUNTER
 
 
typedef enum {
        Attack  = 0,
        Decay   = 1,
        Sustain = 2,
        Release = 3,
} EnvelopePhase;
 
 
#define NUMBER_OF_SID_REGISTERS_FOR_SNAPSHOT    0x20
 
 
struct SidEmulation {
        int sFrameCount;
        unsigned char writtenRegisterValues[NUMBER_OF_SID_REGISTERS_FOR_SNAPSHOT];
        struct SidRegisters {
                struct SidVoice {
                        unsigned short freq;
                        unsigned short pulse;
                        unsigned char wave;
                        unsigned char ad;
                        unsigned char sr;
                } v[3];
                unsigned char ffreqlo;
                unsigned char ffreqhi;
                unsigned char res_ftv;
                unsigned char ftp_vol;
        } sid;
        struct SidOsc {                                         // internal oscillator def
                unsigned long freq;
                unsigned long pulse;
                unsigned char wave;
                unsigned char filter;
                unsigned long attack;
                unsigned long decay;
                unsigned long sustain;
                unsigned long release;
                unsigned long counter;
                // updated envelope generation based on reSID
                unsigned char envelopeOutput;
                signed int currentLFSR;                         // sim counter
                unsigned char zero_lock;
                unsigned char exponential_counter;
                unsigned char envphase;
                unsigned long noisepos;
                unsigned long noiseval;
                unsigned char noiseout;
        } osc[3];
        struct SidFilter {                                      // internal filter def
                int freq;
                unsigned char  l_ena;
                unsigned char  b_ena;
                unsigned char  h_ena;
                unsigned char  v3ena;
                int vol;
                int rez;
                int h;
                int b;
                int l;
        } filter;
        unsigned int sMuteVoice[3];
        unsigned long sCycles;                                  // counter keeps track of burned cpu cycles
        unsigned long sAdsrBugTriggerTime;                      // detection of ADSR-bug conditions
        unsigned long sAdsrBugFrameCount;
        float cyclesPerSample;
        float cycleOverflow;
        // 0x38: supposedly DC level for MOS6581 (whereas it would be 0x80 for the "crappy new chip")
        unsigned level_DC;
#ifdef SID_DEBUG
        unsigned char voiceEnableMask;                          // for debugging: allows to mute certain voices..
#endif
        int limit_LFSR;                                         // the original cycle counter would be 15-bit (but we are counting samples & may rescale the counter accordingly)
        int envelope_counter_period[16];
        int envelope_counter_period_clck[16];
        unsigned long  mixing_frequency;
        unsigned long  freqmul;
        int  filtmul;
        unsigned long cyclesPerSec;
        unsigned long sLastFrameCount;
        unsigned char bval;
        unsigned short wval;
        unsigned long sLastPolledOsc;
        SDL_SpinLock spinlock;
};
 
 
extern void sid_write_reg ( struct SidEmulation *sidemu, int reg, unsigned char val );
extern void sid_init      ( struct SidEmulation *sidemu, unsigned long cyclesPerSec, unsigned long mixfrq );
extern void sid_render    ( struct SidEmulation *sidemu, short *buffer, unsigned long len, int step );
 
#ifdef XEMU_SNAPSHOT_SUPPORT
#include "xemu/emutools_basicdefs.h"
#include "xemu/emutools_snapshot.h"
extern int sid_snapshot_load_state ( const struct xemu_snapshot_definition_st *def , struct xemu_snapshot_block_st *block );
extern int sid_snapshot_save_state ( const struct xemu_snapshot_definition_st *def );
#endif
 
#endif