improved irq handling Cz80_Exec() calls with lots of cycles

[picodrive.git] / Pico / sound / sn76496.c

/***************************************************************************\r
\r
  sn76496.c\r
\r
  Routines to emulate the Texas Instruments SN76489 / SN76496 programmable\r
  tone /noise generator. Also known as (or at least compatible with) TMS9919.\r
\r
  Noise emulation is not accurate due to lack of documentation. The noise\r
  generator uses a shift register with a XOR-feedback network, but the exact\r
  layout is unknown. It can be set for either period or white noise; again,\r
  the details are unknown.\r
\r
  28/03/2005 : Sebastien Chevalier\r
  Update th SN76496Write func, according to SN76489 doc found on SMSPower.\r
   - On write with 0x80 set to 0, when LastRegister is other then TONE,\r
   the function is similar than update with 0x80 set to 1\r
***************************************************************************/\r
\r
#ifndef __GNUC__\r
#pragma warning (disable:4244)\r
#endif\r
\r
#include "sn76496.h"\r
\r
#define MAX_OUTPUT 0x47ff // was 0x7fff\r
\r
#define STEP 0x10000\r
\r
\r
/* Formulas for noise generator */\r
/* bit0 = output */\r
\r
/* noise feedback for white noise mode (verified on real SN76489 by John Kortink) */\r
#define FB_WNOISE 0x14002	/* (16bits) bit16 = bit0(out) ^ bit2 ^ bit15 */\r
\r
/* noise feedback for periodic noise mode */\r
//#define FB_PNOISE 0x10000 /* 16bit rorate */\r
#define FB_PNOISE 0x08000   /* JH 981127 - fixes Do Run Run */\r
\r
/*\r
0x08000 is definitely wrong. The Master System conversion of Marble Madness\r
uses periodic noise as a baseline. With a 15-bit rotate, the bassline is\r
out of tune.\r
The 16-bit rotate has been confirmed against a real PAL Sega Master System 2.\r
Hope that helps the System E stuff, more news on the PSG as and when!\r
*/\r
\r
/* noise generator start preset (for periodic noise) */\r
#define NG_PRESET 0x0f35\r
\r
\r
struct SN76496\r
{\r
	//sound_stream * Channel;\r
	int SampleRate;\r
	unsigned int UpdateStep;\r
	int VolTable[16];	/* volume table         */\r
	int Register[8];	/* registers */\r
	int LastRegister;	/* last register written */\r
	int Volume[4];		/* volume of voice 0-2 and noise */\r
	unsigned int RNG;		/* noise generator      */\r
	int NoiseFB;		/* noise feedback mask */\r
	int Period[4];\r
	int Count[4];\r
	int Output[4];\r
	int pad[1];\r
};\r
\r
static struct SN76496 ono_sn; // one and only SN76496\r
int *sn76496_regs;\r
\r
//static\r
void SN76496Write(int data)\r
{\r
	struct SN76496 *R = &ono_sn;\r
	int n;\r
\r
\r
	/* update the output buffer before changing the registers */\r
	//stream_update(R->Channel,0);\r
\r
	if (data & 0x80)\r
	{\r
		int r = (data & 0x70) >> 4;\r
		int c = r/2;\r
\r
		R->LastRegister = r;\r
		R->Register[r] = (R->Register[r] & 0x3f0) | (data & 0x0f);\r
		switch (r)\r
		{\r
			case 0:	/* tone 0 : frequency */\r
			case 2:	/* tone 1 : frequency */\r
			case 4:	/* tone 2 : frequency */\r
				R->Period[c] = R->UpdateStep * R->Register[r];\r
				if (R->Period[c] == 0) R->Period[c] = R->UpdateStep;\r
				if (r == 4)\r
				{\r
					/* update noise shift frequency */\r
					if ((R->Register[6] & 0x03) == 0x03)\r
						R->Period[3] = 2 * R->Period[2];\r
				}\r
				break;\r
			case 1:	/* tone 0 : volume */\r
			case 3:	/* tone 1 : volume */\r
			case 5:	/* tone 2 : volume */\r
			case 7:	/* noise  : volume */\r
				R->Volume[c] = R->VolTable[data & 0x0f];\r
				break;\r
			case 6:	/* noise  : frequency, mode */\r
				{\r
					int n = R->Register[6];\r
					R->NoiseFB = (n & 4) ? FB_WNOISE : FB_PNOISE;\r
					n &= 3;\r
					/* N/512,N/1024,N/2048,Tone #3 output */\r
					R->Period[3] = ((n&3) == 3) ? 2 * R->Period[2] : (R->UpdateStep << (5+(n&3)));\r
\r
					/* reset noise shifter */\r
					R->RNG = NG_PRESET;\r
					R->Output[3] = R->RNG & 1;\r
				}\r
				break;\r
		}\r
	}\r
	else\r
	{\r
		int r = R->LastRegister;\r
		int c = r/2;\r
\r
		switch (r)\r
		{\r
			case 0:	/* tone 0 : frequency */\r
			case 2:	/* tone 1 : frequency */\r
			case 4:	/* tone 2 : frequency */\r
				R->Register[r] = (R->Register[r] & 0x0f) | ((data & 0x3f) << 4);\r
				R->Period[c] = R->UpdateStep * R->Register[r];\r
				if (R->Period[c] == 0) R->Period[c] = R->UpdateStep;\r
				if (r == 4)\r
				{\r
					/* update noise shift frequency */\r
					if ((R->Register[6] & 0x03) == 0x03)\r
						R->Period[3] = 2 * R->Period[2];\r
				}\r
				break;\r
			case 1:	/* tone 0 : volume */\r
			case 3:	/* tone 1 : volume */\r
			case 5:	/* tone 2 : volume */\r
			case 7:	/* noise  : volume */\r
				R->Volume[c] = R->VolTable[data & 0x0f];\r
				R->Register[r] = (R->Register[r] & 0x3f0) | (data & 0x0f);\r
				break;\r
			case 6:	/* noise  : frequency, mode */\r
				{\r
					R->Register[r] = (R->Register[r] & 0x3f0) | (data & 0x0f);\r
					n = R->Register[6];\r
					R->NoiseFB = (n & 4) ? FB_WNOISE : FB_PNOISE;\r
					n &= 3;\r
					/* N/512,N/1024,N/2048,Tone #3 output */\r
					R->Period[3] = ((n&3) == 3) ? 2 * R->Period[2] : (R->UpdateStep << (5+(n&3)));\r
\r
					/* reset noise shifter */\r
					R->RNG = NG_PRESET;\r
					R->Output[3] = R->RNG & 1;\r
				}\r
				break;\r
		}\r
	}\r
}\r
\r
/*\r
WRITE8_HANDLER( SN76496_0_w ) {	SN76496Write(0,data); }\r
WRITE8_HANDLER( SN76496_1_w ) {	SN76496Write(1,data); }\r
WRITE8_HANDLER( SN76496_2_w ) {	SN76496Write(2,data); }\r
WRITE8_HANDLER( SN76496_3_w ) {	SN76496Write(3,data); }\r
WRITE8_HANDLER( SN76496_4_w ) {	SN76496Write(4,data); }\r
*/\r
\r
//static\r
void SN76496Update(short *buffer, int length, int stereo)\r
{\r
	int i;\r
	struct SN76496 *R = &ono_sn;\r
\r
	/* If the volume is 0, increase the counter */\r
	for (i = 0;i < 4;i++)\r
	{\r
		if (R->Volume[i] == 0)\r
		{\r
			/* note that I do count += length, NOT count = length + 1. You might think */\r
			/* it's the same since the volume is 0, but doing the latter could cause */\r
			/* interferencies when the program is rapidly modulating the volume. */\r
			if (R->Count[i] <= length*STEP) R->Count[i] += length*STEP;\r
		}\r
	}\r
\r
	while (length > 0)\r
	{\r
		int vol[4];\r
		unsigned int out;\r
		int left;\r
\r
\r
		/* vol[] keeps track of how long each square wave stays */\r
		/* in the 1 position during the sample period. */\r
		vol[0] = vol[1] = vol[2] = vol[3] = 0;\r
\r
		for (i = 0;i < 3;i++)\r
		{\r
			if (R->Output[i]) vol[i] += R->Count[i];\r
			R->Count[i] -= STEP;\r
			/* Period[i] is the half period of the square wave. Here, in each */\r
			/* loop I add Period[i] twice, so that at the end of the loop the */\r
			/* square wave is in the same status (0 or 1) it was at the start. */\r
			/* vol[i] is also incremented by Period[i], since the wave has been 1 */\r
			/* exactly half of the time, regardless of the initial position. */\r
			/* If we exit the loop in the middle, Output[i] has to be inverted */\r
			/* and vol[i] incremented only if the exit status of the square */\r
			/* wave is 1. */\r
			while (R->Count[i] <= 0)\r
			{\r
				R->Count[i] += R->Period[i];\r
				if (R->Count[i] > 0)\r
				{\r
					R->Output[i] ^= 1;\r
					if (R->Output[i]) vol[i] += R->Period[i];\r
					break;\r
				}\r
				R->Count[i] += R->Period[i];\r
				vol[i] += R->Period[i];\r
			}\r
			if (R->Output[i]) vol[i] -= R->Count[i];\r
		}\r
\r
		left = STEP;\r
		do\r
		{\r
			int nextevent;\r
\r
			if (R->Count[3] < left) nextevent = R->Count[3];\r
			else nextevent = left;\r
\r
			if (R->Output[3]) vol[3] += R->Count[3];\r
			R->Count[3] -= nextevent;\r
			if (R->Count[3] <= 0)\r
			{\r
				if (R->RNG & 1) R->RNG ^= R->NoiseFB;\r
				R->RNG >>= 1;\r
				R->Output[3] = R->RNG & 1;\r
				R->Count[3] += R->Period[3];\r
				if (R->Output[3]) vol[3] += R->Period[3];\r
			}\r
			if (R->Output[3]) vol[3] -= R->Count[3];\r
\r
			left -= nextevent;\r
		} while (left > 0);\r
\r
		out = vol[0] * R->Volume[0] + vol[1] * R->Volume[1] +\r
				vol[2] * R->Volume[2] + vol[3] * R->Volume[3];\r
\r
		if (out > MAX_OUTPUT * STEP) out = MAX_OUTPUT * STEP;\r
\r
		if ((out /= STEP)) // will be optimized to shift; max 0x47ff = 18431\r
			*buffer += out;\r
		if(stereo) buffer+=2; // only left for stereo, to be mixed to right later\r
		else buffer++;\r
\r
		length--;\r
	}\r
}\r
\r
\r
static void SN76496_set_clock(struct SN76496 *R,int clock)\r
{\r
\r
	/* the base clock for the tone generators is the chip clock divided by 16; */\r
	/* for the noise generator, it is clock / 256. */\r
	/* Here we calculate the number of steps which happen during one sample */\r
	/* at the given sample rate. No. of events = sample rate / (clock/16). */\r
	/* STEP is a multiplier used to turn the fraction into a fixed point */\r
	/* number. */\r
	R->UpdateStep = ((double)STEP * R->SampleRate * 16) / clock;\r
}\r
\r
\r
static void SN76496_set_gain(struct SN76496 *R,int gain)\r
{\r
	int i;\r
	double out;\r
\r
\r
	gain &= 0xff;\r
\r
	/* increase max output basing on gain (0.2 dB per step) */\r
	out = MAX_OUTPUT / 3;\r
	while (gain-- > 0)\r
		out *= 1.023292992;	/* = (10 ^ (0.2/20)) */\r
\r
	/* build volume table (2dB per step) */\r
	for (i = 0;i < 15;i++)\r
	{\r
		/* limit volume to avoid clipping */\r
		if (out > MAX_OUTPUT / 3) R->VolTable[i] = MAX_OUTPUT / 3;\r
		else R->VolTable[i] = out;\r
\r
		out /= 1.258925412;	/* = 10 ^ (2/20) = 2dB */\r
	}\r
	R->VolTable[15] = 0;\r
}\r
\r
\r
//static\r
int SN76496_init(int clock,int sample_rate)\r
{\r
	struct SN76496 *R = &ono_sn;\r
	int i;\r
\r
	//R->Channel = stream_create(0,1, sample_rate,R,SN76496Update);\r
	sn76496_regs = R->Register;\r
\r
	R->SampleRate = sample_rate;\r
	SN76496_set_clock(R,clock);\r
\r
	for (i = 0;i < 4;i++) R->Volume[i] = 0;\r
\r
	R->LastRegister = 0;\r
	for (i = 0;i < 8;i+=2)\r
	{\r
		R->Register[i] = 0;\r
		R->Register[i + 1] = 0x0f;	/* volume = 0 */\r
	}\r
\r
	for (i = 0;i < 4;i++)\r
	{\r
		R->Output[i] = 0;\r
		R->Period[i] = R->Count[i] = R->UpdateStep;\r
	}\r
	R->RNG = NG_PRESET;\r
	R->Output[3] = R->RNG & 1;\r
\r
	// added\r
	SN76496_set_gain(R, 0);\r
\r
	return 0;\r
}\r
\r