mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
synced 2024-12-29 12:41:48 +01:00
1cfb7e6f44
+optimized SN76489 core +added configurable SN76489 Noise boost +added savestate version check
80 lines
2.8 KiB
C
80 lines
2.8 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 (Genesis Plus GX)
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- Removed stereo GG support (unused)
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- Rade SN76489_Update outputs 16bits mono samples
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- Replaced volume table with VGM plugin's one
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05/01/09 Eke-Eke (Genesis Plus GX)
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- Modified Cut-Off frequency (according to Steve Snake: http://www.smspower.org/forums/viewtopic.php?t=1746)
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25/05/09 Eke-Eke (Genesis Plus GX)
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- Removed multichip support (unused)
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- Removed alternate volume table, panning & mute support (unused)
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- Removed configurable Feedback and Shift Register Width (always use Sega ones)
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- Added linear resampling using Blip Buffer (Blargg's implementation: http://www.smspower.org/forums/viewtopic.php?t=11376)
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*/
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#ifndef _SN76489_H_
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#define _SN76489_H_
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/* SN76489 clone in Sega's VDP chips (315-5124, 315-5246, 315-5313, Game Gear) */
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#define FB_SEGAVDP 0x0009
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#define SRW_SEGAVDP 16
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typedef struct
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{
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/* Configuration */
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int BoostNoise; // double noise volume when non-zero
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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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/* Blip-Buffer variables */
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struct blip_buffer_t* blip_buffer; /* delta resampler */
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int chan_amp[4]; /* current channel amplitudes in delta buffers */
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} SN76489_Context;
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/* Function prototypes */
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extern void SN76489_Init(int PSGClockValue, int SamplingRate);
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extern void SN76489_Reset(void);
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extern void SN76489_Shutdown(void);
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extern void SN76489_SetContext(uint8 *data);
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extern void SN76489_GetContext(uint8 *data);
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extern uint8 *SN76489_GetContextPtr(void);
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extern int SN76489_GetContextSize(void);
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extern void SN76489_Write(int data);
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extern void SN76489_Update(INT16 *buffer, int length);
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extern void SN76489_BoostNoise(int boost);
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#endif /* _SN76489_H_ */
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