mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
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105 lines
3.6 KiB
C
105 lines
3.6 KiB
C
/*
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SN76489 emulation
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by Maxim in 2001 and 2002
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converted from my original Delphi implementation
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I'm a C newbie so I'm sure there are loads of stupid things
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in here which I'll come back to some day and redo
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Includes:
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- Super-high quality tone channel "oversampling" by calculating fractional positions on transitions
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- Noise output pattern reverse engineered from actual SMS output
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- Volume levels taken from actual SMS output
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07/08/04 Charles MacDonald
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Modified for use with SMS Plus:
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- Added support for multiple PSG chips.
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- Added reset/config/update routines.
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- Added context management routines.
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- Removed SN76489_GetValues().
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- Removed some unused variables.
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25/04/07 Eke-Eke
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Modified for use with GenesisPlus Gamecube's port:
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- made SN76489_Update outputs 16bits mono samples
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- replaced volume table with VGM plugin's one
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*/
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#ifndef _SN76489_H_
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#define _SN76489_H_
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#define MAX_SN76489 4
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/*
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More testing is needed to find and confirm feedback patterns for
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SN76489 variants and compatible chips.
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*/
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enum feedback_patterns {
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FB_BBCMICRO = 0x8005, /* Texas Instruments TMS SN76489N (original) from BBC Micro computer */
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FB_SC3000 = 0x0006, /* Texas Instruments TMS SN76489AN (rev. A) from SC-3000H computer */
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FB_SEGAVDP = 0x0009, /* SN76489 clone in Sega's VDP chips (315-5124, 315-5246, 315-5313, Game Gear) */
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};
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enum sr_widths {
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SRW_SC3000BBCMICRO = 15,
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SRW_SEGAVDP = 16
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};
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enum volume_modes {
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VOL_TRUNC = 0, /* Volume levels 13-15 are identical */
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VOL_FULL = 1, /* Volume levels 13-15 are unique */
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};
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enum mute_values {
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MUTE_ALLOFF = 0, /* All channels muted */
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MUTE_TONE1 = 1, /* Tone 1 mute control */
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MUTE_TONE2 = 2, /* Tone 2 mute control */
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MUTE_TONE3 = 4, /* Tone 3 mute control */
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MUTE_NOISE = 8, /* Noise mute control */
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MUTE_ALLON = 15, /* All channels enabled */
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};
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typedef struct
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{
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int Mute; // per-channel muting
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int VolumeArray;
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int BoostNoise; // double noise volume when non-zero
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/* Variables */
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float Clock;
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float dClock;
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int PSGStereo;
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int NumClocksForSample;
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int WhiteNoiseFeedback;
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int SRWidth;
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/* PSG registers: */
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int Registers[8]; /* Tone, vol x4 */
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int LatchedRegister;
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int NoiseShiftRegister;
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int NoiseFreq; /* Noise channel signal generator frequency */
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/* Output calculation variables */
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int ToneFreqVals[4]; /* Frequency register values (counters) */
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int ToneFreqPos[4]; /* Frequency channel flip-flops */
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int Channels[4]; /* Value of each channel, before stereo is applied */
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float IntermediatePos[4]; /* intermediate values used at boundaries between + and - (does not need double accuracy)*/
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int panning[4]; /* fake stereo - 0..127..254 */
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} SN76489_Context;
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/* Function prototypes */
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extern void SN76489_Init(int which, int PSGClockValue, int SamplingRate);
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extern void SN76489_Reset(int which);
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extern void SN76489_Config(int which, int mute, int volume, int feedback, int sw_width, int boost_noise);
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extern void SN76489_SetContext(int which, uint8 *data);
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extern void SN76489_GetContext(int which, uint8 *data);
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extern uint8 *SN76489_GetContextPtr(int which);
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extern int SN76489_GetContextSize(void);
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extern void SN76489_Write(int which, int data);
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extern void SN76489_Update(int which, INT16 *buffer, int length);
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#endif /* _SN76489_H_ */
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