Genesis-Plus-GX/source/sound/sn76489.h

105 lines
3.6 KiB
C
Raw Normal View History

2008-08-07 14:26:07 +02:00
/*
SN76489 emulation
by Maxim in 2001 and 2002
converted from my original Delphi implementation
I'm a C newbie so I'm sure there are loads of stupid things
in here which I'll come back to some day and redo
Includes:
- Super-high quality tone channel "oversampling" by calculating fractional positions on transitions
- Noise output pattern reverse engineered from actual SMS output
- Volume levels taken from actual SMS output
07/08/04 Charles MacDonald
Modified for use with SMS Plus:
- Added support for multiple PSG chips.
- Added reset/config/update routines.
- Added context management routines.
- Removed SN76489_GetValues().
- Removed some unused variables.
25/04/07 Eke-Eke
Modified for use with GenesisPlus Gamecube's port:
- made SN76489_Update outputs 16bits mono samples
- replaced volume table with VGM plugin's one
*/
#ifndef _SN76489_H_
#define _SN76489_H_
#define MAX_SN76489 4
/*
More testing is needed to find and confirm feedback patterns for
SN76489 variants and compatible chips.
*/
enum feedback_patterns {
FB_BBCMICRO = 0x8005, /* Texas Instruments TMS SN76489N (original) from BBC Micro computer */
FB_SC3000 = 0x0006, /* Texas Instruments TMS SN76489AN (rev. A) from SC-3000H computer */
FB_SEGAVDP = 0x0009, /* SN76489 clone in Sega's VDP chips (315-5124, 315-5246, 315-5313, Game Gear) */
};
enum sr_widths {
SRW_SC3000BBCMICRO = 15,
SRW_SEGAVDP = 16
};
enum volume_modes {
VOL_TRUNC = 0, /* Volume levels 13-15 are identical */
VOL_FULL = 1, /* Volume levels 13-15 are unique */
};
enum mute_values {
MUTE_ALLOFF = 0, /* All channels muted */
MUTE_TONE1 = 1, /* Tone 1 mute control */
MUTE_TONE2 = 2, /* Tone 2 mute control */
MUTE_TONE3 = 4, /* Tone 3 mute control */
MUTE_NOISE = 8, /* Noise mute control */
MUTE_ALLON = 15, /* All channels enabled */
};
typedef struct
{
int Mute; // per-channel muting
int VolumeArray;
int BoostNoise; // double noise volume when non-zero
/* Variables */
float Clock;
float dClock;
int PSGStereo;
int NumClocksForSample;
int WhiteNoiseFeedback;
int SRWidth;
/* PSG registers: */
int Registers[8]; /* Tone, vol x4 */
int LatchedRegister;
int NoiseShiftRegister;
int NoiseFreq; /* Noise channel signal generator frequency */
/* Output calculation variables */
int ToneFreqVals[4]; /* Frequency register values (counters) */
int ToneFreqPos[4]; /* Frequency channel flip-flops */
int Channels[4]; /* Value of each channel, before stereo is applied */
float IntermediatePos[4]; /* intermediate values used at boundaries between + and - (does not need double accuracy)*/
int panning[4]; /* fake stereo - 0..127..254 */
} SN76489_Context;
/* Function prototypes */
extern void SN76489_Init(int which, int PSGClockValue, int SamplingRate);
extern void SN76489_Reset(int which);
extern void SN76489_Config(int which, int mute, int volume, int feedback, int sw_width, int boost_noise);
extern void SN76489_SetContext(int which, uint8 *data);
extern void SN76489_GetContext(int which, uint8 *data);
extern uint8 *SN76489_GetContextPtr(int which);
extern int SN76489_GetContextSize(void);
extern void SN76489_Write(int which, int data);
extern void SN76489_Update(int which, INT16 *buffer, int length);
#endif /* _SN76489_H_ */