+++ /dev/null
-//
-// AY-3-8910 Emulator
-//
-// This was written mainly from the General Instruments datasheet for the 8910
-// part. I would have used the one from MAME, but it was so poorly written and
-// so utterly incomprehensible that I decided to start from scratch to see if I
-// could do any better; and so here we are. I did use a bit of code from
-// MAME's AY-3-8910 RNG, as it was just too neat not to use. :-)
-//
-// by James Hammons
-// (C) 2018 Underground Software
-//
-
-#include "ay8910.h"
-
-#include <string.h> // for memset()
-#include "log.h"
-#include "sound.h"
-
-
-struct AY_3_8910
-{
- // User visible registers
- uint16_t period[3]; // Channel A-C period
- int16_t volume[3]; // Channel A-C volume (non-envelope mode)
- bool envEnable[3]; // Channel A-C envelope enable
- bool toneEnable[3]; // Channel A-C tone enable
- bool noiseEnable[3]; // Channel A-C noise enable
- uint16_t noisePeriod; // Noise period (5 bits * 16)
- uint32_t envPeriod; // Envelope period (16 bits * 256)
- bool envAttack; // Envelope Attack bit
- bool envAlternate; // Envelope Alternate bit
- bool envHold; // Envelope Hold bit
- // Internal registers
- uint16_t count[3]; // Channel A-C current count
- bool state[3]; // Channel A-C current state
- uint16_t noiseCount; // Noise current count
- bool noiseState; // Noise state
- uint32_t envCount[3]; // Envelope current count
- int16_t envDirection[3];// Envelope direction (rising, 0, or falling)
- uint32_t prng; // Psuedo RNG (17 bits)
-};
-
-
-// Maximum volume that can be generated by one voice
-float maxVolume = 8192.0f;
-
-// Normalized volumes (zero to one) for AY-3-8910 output, in 16 steps
-static float normalizedVolume[16];// = {};
-
-// AY-3-8910 register IDs
-enum { AY_AFINE = 0, AY_ACOARSE, AY_BFINE, AY_BCOARSE, AY_CFINE, AY_CCOARSE,
- AY_NOISEPER, AY_ENABLE, AY_AVOL, AY_BVOL, AY_CVOL, AY_EFINE, AY_ECOARSE,
- AY_ESHAPE, AY_PORTA, AY_PORTB };
-
-// Chip structs (for up to four separate chips)
-static AY_3_8910 ay[4];
-
-
-void AYInit(void)
-{
- for(int chip=0; chip<4; chip++)
- AYReset(chip);
-
- // Our normalized volume levels are from 0 to -48 dB, in 3 dB steps.
- // N.B.: It's 3dB steps because those sound the best. Dunno what it really
- // is, as nothing in the documentation tells you (it only says that
- // each channel's volume is normalized from 0 to 1.0V).
- float level = 1.0f;
-
- for(int i=15; i>=0; i--)
- {
- normalizedVolume[i] = level;
- level /= 1.4125375446228; // 10.0 ^ (3.0 / 20.0) = 3 dB
- }
-
- // In order to get a scale that goes from 0 to 1 smoothly, we renormalize
- // our volumes so that volume[0] is actually 0, and volume[15] is 1.
- // Basically, we're sliding the curve down the Y-axis so that volume[0]
- // touches the X-axis, then stretching the result so that it fits into the
- // interval (0, 1).
- float vol0 = normalizedVolume[0];
- float vol15 = normalizedVolume[15] - vol0;
-
- for(int i=0; i<16; i++)
- normalizedVolume[i] = (normalizedVolume[i] - vol0) / vol15;
-
-#if 0
- WriteLog("\nRenormalized volume, level (max=%d):\n", (int)maxVolume);
- for(int i=0; i<16; i++)
- WriteLog("%lf, %d\n", normalizedVolume[i], (int)(normalizedVolume[i] * maxVolume));
- WriteLog("\n");
-#endif
-}
-/*
-Renormalized:
-0.000000, 0
-0.002333, 13
-0.005628, 33
-0.010283, 61
-0.016859, 101
-0.026146, 156
-0.039266, 235
-0.057797, 346
-0.083974, 503
-0.120949, 725
-0.173178, 1039
-0.246954, 1481
-0.351165, 2106
-0.498366, 2990
-0.706294, 4237
-1.000000, 6000
-*/
-
-
-void AYReset(int chipNum)
-{
- memset(&ay[chipNum], 0, sizeof(struct AY_3_8910));
- ay[chipNum].prng = 1; // Set correct PRNG seed
-}
-
-
-void AYWrite(int chipNum, int reg, int value)
-{
-#if 0
-static char regname[16][32] = {
- "AY_AFINE ",
- "AY_ACOARSE ",
- "AY_BFINE ",
- "AY_BCOARSE ",
- "AY_CFINE ",
- "AY_CCOARSE ",
- "AY_NOISEPER",
- "AY_ENABLE ",
- "AY_AVOL ",
- "AY_BVOL ",
- "AY_CVOL ",
- "AY_EFINE ",
- "AY_ECOARSE ",
- "AY_ESHAPE ",
- "AY_PORTA ",
- "AY_PORTB "
-};
-WriteLog("*** AY(%d) Reg: %s = $%02X\n", chipNum, regname[reg], value);
-#endif
- AY_3_8910 * chip = &ay[chipNum];
- value &= 0xFF; // Ensure passed in value is no larger than 8 bits
-
- switch (reg)
- {
- case AY_AFINE:
- // The square wave period is the passed in value times 16, so we handle
- // that here.
- chip->period[0] = (chip->period[0] & 0xF000) | (value << 4);
- break;
- case AY_ACOARSE:
- chip->period[0] = ((value & 0x0F) << 12) | (chip->period[0] & 0xFF0);
- break;
- case AY_BFINE:
- chip->period[1] = (chip->period[1] & 0xF000) | (value << 4);
- break;
- case AY_BCOARSE:
- chip->period[1] = ((value & 0x0F) << 12) | (chip->period[1] & 0xFF0);
- break;
- case AY_CFINE:
- chip->period[2] = (chip->period[2] & 0xF000) | (value << 4);
- break;
- case AY_CCOARSE:
- chip->period[2] = ((value & 0x0F) << 12) | (chip->period[2] & 0xFF0);
- break;
- case AY_NOISEPER:
- // Like the square wave period, the value is the what's passed * 16.
- chip->noisePeriod = (value & 0x1F) << 4;
- break;
- case AY_ENABLE:
- chip->toneEnable[0] = (value & 0x01 ? false : true);
- chip->toneEnable[1] = (value & 0x02 ? false : true);
- chip->toneEnable[2] = (value & 0x04 ? false : true);
- chip->noiseEnable[0] = (value & 0x08 ? false : true);
- chip->noiseEnable[1] = (value & 0x10 ? false : true);
- chip->noiseEnable[2] = (value & 0x20 ? false : true);
- break;
- case AY_AVOL:
- chip->volume[0] = value & 0x0F;
- chip->envEnable[0] = (value & 0x10 ? true : false);
-
- if (chip->envEnable[0])
- {
- chip->envCount[0] = 0;
- chip->volume[0] = (chip->envAttack ? 0 : 15);
- chip->envDirection[0] = (chip->envAttack ? 1 : -1);
- }
- break;
- case AY_BVOL:
- chip->volume[1] = value & 0x0F;
- chip->envEnable[1] = (value & 0x10 ? true : false);
-
- if (chip->envEnable[1])
- {
- chip->envCount[1] = 0;
- chip->volume[1] = (chip->envAttack ? 0 : 15);
- chip->envDirection[1] = (chip->envAttack ? 1 : -1);
- }
- break;
- case AY_CVOL:
- chip->volume[2] = value & 0x0F;
- chip->envEnable[2] = (value & 0x10 ? true : false);
-
- if (chip->envEnable[2])
- {
- chip->envCount[2] = 0;
- chip->volume[2] = (chip->envAttack ? 0 : 15);
- chip->envDirection[2] = (chip->envAttack ? 1 : -1);
- }
- break;
- case AY_EFINE:
- // The envelope period is 256 times the passed in value
- chip->envPeriod = (chip->envPeriod & 0xFF0000) | (value << 8);
- break;
- case AY_ECOARSE:
- chip->envPeriod = (value << 16) | (chip->envPeriod & 0xFF00);
- break;
- case AY_ESHAPE:
- chip->envAttack = (value & 0x04 ? true : false);
- chip->envAlternate = (value & 0x02 ? true : false);
- chip->envHold = (value & 0x01 ? true : false);
-
- // If the Continue bit is *not* set, the Alternate bit is forced to the
- // Attack bit, and Hold is forced on.
- if (!(value & 0x08))
- {
- chip->envAlternate = chip->envAttack;
- chip->envHold = true;
- }
-
- // Reset all voice envelope counts...
- for(int i=0; i<3; i++)
- {
- chip->envCount[i] = 0;
- chip->envDirection[i] = (chip->envAttack ? 1 : -1);
-
- // Only reset the volume if the envelope is enabled!
- if (chip->envEnable[i])
- chip->volume[i] = (chip->envAttack ? 0 : 15);
- }
- break;
- }
-}
-
-
-//
-// Generate one sample and quit
-//
-bool logAYInternal = false;
-uint16_t AYGetSample(int chipNum)
-{
- AY_3_8910 * chip = &ay[chipNum];
- uint16_t sample = 0;
-
- // Number of cycles per second to run the PSG is the 6502 clock rate
- // divided by the host sample rate
- const static double exactCycles = 1020484.32 / (double)SAMPLE_RATE;
- static double overflow = 0;
-
- int fullCycles = (int)exactCycles;
- overflow += exactCycles - (double)fullCycles;
-
- if (overflow >= 1.0)
- {
- fullCycles++;
- overflow -= 1.0;
- }
-
- for(int i=0; i<fullCycles; i++)
- {
- for(int j=0; j<3; j++)
- {
- // Tone generators only run if the corresponding voice is enabled.
- // N.B.: We also reject any period set that is less than 2.
- if (chip->toneEnable[j] && (chip->period[j] > 16))
- {
- chip->count[j]++;
-
- // It's (period / 2) because one full period of a square wave
- // is 0 for half of its period and 1 for the other half!
- if (chip->count[j] > (chip->period[j] / 2))
- {
- chip->count[j] = 0;
- chip->state[j] = !chip->state[j];
- }
- }
-
- // Envelope generator only runs if the corresponding voice flag is
- // enabled.
- if (chip->envEnable[j])
- {
- chip->envCount[j]++;
-
- // It's (EP / 16) because there are 16 volume steps in each EP.
- if (chip->envCount[j] > (chip->envPeriod / 16))
- {
- // Attack 0 = \, 1 = / (attack lasts one EP)
- // Alternate = mirror envelope's last attack
- // Hold = run 1 EP, hold at level (Alternate XOR Attack)
- chip->envCount[j] = 0;
-
- // We've hit a point where we need to make a change to the
- // envelope's volume, so do it:
- chip->volume[j] += chip->envDirection[j];
-
- // If we hit the end of the EP, change the state of the
- // envelope according to the envelope's variables.
- if ((chip->volume[j] > 15) || (chip->volume[j] < 0))
- {
- // Hold means we set the volume to (Alternate XOR
- // Attack) and stay there after the Attack EP.
- if (chip->envHold)
- {
- chip->volume[j] = (chip->envAttack != chip->envAlternate ? 15: 0);
- chip->envDirection[j] = 0;
- }
- else
- {
- // If the Alternate bit is set, we mirror the
- // Attack pattern; otherwise we reset it to the
- // whatever level was set by the Attack bit.
- if (chip->envAlternate)
- {
- chip->envDirection[j] = -chip->envDirection[j];
- chip->volume[j] += chip->envDirection[j];
- }
- else
- chip->volume[j] = (chip->envAttack ? 0 : 15);
- }
- }
- }
- }
- }
-
- // Noise generator (the PRNG) runs all the time:
- chip->noiseCount++;
-
- if (chip->noiseCount > chip->noisePeriod)
- {
- chip->noiseCount = 0;
-
- // The following is from MAME's AY-3-8910 code:
- // The Pseudo Random Number Generator of the 8910 is a 17-bit shift
- // register. The input to the shift register is bit0 XOR bit3 (bit0
- // is the output). This was verified on AY-3-8910 and YM2149 chips.
-
- // The following is a fast way to compute bit17 = bit0 ^ bit3.
- // Instead of doing all the logic operations, we only check bit0,
- // relying on the fact that after three shifts of the register,
- // what now is bit3 will become bit0, and will invert, if
- // necessary, bit14, which previously was bit17.
- if (chip->prng & 0x00001)
- {
- // This version is called the "Galois configuration".
- chip->prng ^= 0x24000;
- // The noise wave *toggles* when a one shows up in bit0...
- chip->noiseState = !chip->noiseState;
- }
-
- chip->prng >>= 1;
- }
- }
-
- // We mix channels A-C here into one sample, because the Mockingboard just
- // sums the output of the AY-3-8910 by tying their lines together.
- // We also handle the various cases (of which there are four) of mixing
- // pure tones and "noise" tones together.
- for(int i=0; i<3; i++)
- {
- // Set the volume level scaled by the maximum volume (which can be
- // altered outside of this module).
- int level = (int)(normalizedVolume[chip->volume[i]] * maxVolume);
-
- if (chip->toneEnable[i] && !chip->noiseEnable[i])
- sample += (chip->state[i] ? level : 0);
- else if (!chip->toneEnable[i] && chip->noiseEnable[i])
- sample += (chip->noiseState ? level : 0);
- else if (chip->toneEnable[i] && chip->noiseEnable[i])
- sample += (chip->state[i] & chip->noiseState ? level : 0);
- else if (!chip->toneEnable[i] && !chip->noiseEnable[i])
- sample += level;
- }
-
- if (logAYInternal)
- {
- WriteLog(" (%d) State A,B,C: %s %s %s, Sample: $%04X, P: $%X, $%X, $%X\n", chipNum, (chip->state[0] ? "1" : "0"), (chip->state[1] ? "1" : "0"), (chip->state[2] ? "1" : "0"), sample, chip->period[0], chip->period[1], chip->period[2]);
- }
-
- return sample;
-}
-
-
-
-
-
-// STUFF TO DELETE...
-
-#if 0
-
-/***************************************************************************
-
- ay8910.cpp
-
- Emulation of the AY-3-8910 / YM2149 sound chip.
-
- Based on various code snippets by Ville Hallik, Michael Cuddy,
- Tatsuyuki Satoh, Fabrice Frances, Nicola Salmoria.
-
-***************************************************************************/
-
-//
-// From mame.txt (http://www.mame.net/readme.html)
-//
-// VI. Reuse of Source Code
-// --------------------------
-// This chapter might not apply to specific portions of MAME (e.g. CPU
-// emulators) which bear different copyright notices.
-// The source code cannot be used in a commercial product without the
-// written authorization of the authors. Use in non-commercial products is
-// allowed, and indeed encouraged. If you use portions of the MAME source
-// code in your program, however, you must make the full source code freely
-// available as well.
-// Usage of the _information_ contained in the source code is free for any
-// use. However, given the amount of time and energy it took to collect this
-// information, if you find new information we would appreciate if you made
-// it freely available as well.
-//
-
-// JLH: Commented out MAME specific crap
-
-#define MAX_OUTPUT 0x7FFF
-
-// See AY8910_set_clock() for definition of STEP
-#define STEP 0x8000
-
-struct AY8910
-{
- int Channel;
- int SampleRate;
- int register_latch;
- unsigned char Regs[16];
- unsigned int UpdateStep;
- int PeriodA, PeriodB, PeriodC, PeriodN, PeriodE;
- int CountA, CountB, CountC, CountN, CountE;
- unsigned int VolA, VolB, VolC, VolE;
- unsigned char EnvelopeA, EnvelopeB, EnvelopeC;
- unsigned char OutputA, OutputB, OutputC, OutputN;
- signed char CountEnv;
- unsigned char Hold, Alternate, Attack, Holding;
- int RNG;
- unsigned int VolTable[32];
-};
-
-static struct AY8910 AYPSG[MAX_8910]; /* array of PSG's */
-
-#define AY_AFINE (0)
-#define AY_ACOARSE (1)
-#define AY_BFINE (2)
-#define AY_BCOARSE (3)
-#define AY_CFINE (4)
-#define AY_CCOARSE (5)
-#define AY_NOISEPER (6)
-#define AY_ENABLE (7)
-#define AY_AVOL (8)
-#define AY_BVOL (9)
-#define AY_CVOL (10)
-#define AY_EFINE (11)
-#define AY_ECOARSE (12)
-#define AY_ESHAPE (13)
-//#define AY_PORTA (14)
-//#define AY_PORTB (15)
-
-
-void _AYWriteReg(int n, int r, int v)
-{
-#if 1
-static char regname[16][32] = {
-"AY_AFINE ",
-"AY_ACOARSE ",
-"AY_BFINE ",
-"AY_BCOARSE ",
-"AY_CFINE ",
-"AY_CCOARSE ",
-"AY_NOISEPER",
-"AY_ENABLE ",
-"AY_AVOL ",
-"AY_BVOL ",
-"AY_CVOL ",
-"AY_EFINE ",
-"AY_ECOARSE ",
-"AY_ESHAPE ",
-"AY_PORTA ",
-"AY_PORTB "
-};
-WriteLog("*** AY(%d) Reg: %s = $%02X\n", n, regname[r], v);
-#endif
- struct AY8910 * PSG = &AYPSG[n];
- int old;
-
- PSG->Regs[r] = v;
-
- /* A note about the period of tones, noise and envelope: for speed reasons,
- * we count down from the period to 0, but careful studies of the chip
- * output prove that it instead counts up from 0 until the counter becomes
- * greater or equal to the period. This is an important difference when the
- * program is rapidly changing the period to modulate the sound.
- * To compensate for the difference, when the period is changed we adjust
- * our internal counter.
- * Also, note that period = 0 is the same as period = 1. This is mentioned
- * in the YM2203 data sheets. However, this does NOT apply to the Envelope
- * period. In that case, period = 0 is half as period = 1. */
- switch (r)
- {
- case AY_AFINE:
- case AY_ACOARSE:
- PSG->Regs[AY_ACOARSE] &= 0x0F;
- old = PSG->PeriodA;
-// PSG->PeriodA = (PSG->Regs[AY_AFINE] + 256 * PSG->Regs[AY_ACOARSE]) * PSG->UpdateStep;
- PSG->PeriodA = ((PSG->Regs[AY_ACOARSE] << 8) | PSG->Regs[AY_AFINE]) * PSG->UpdateStep;
-
- if (PSG->PeriodA == 0)
- PSG->PeriodA = PSG->UpdateStep;
-
- PSG->CountA += PSG->PeriodA - old;
-
- if (PSG->CountA <= 0)
- PSG->CountA = 1;
- break;
- case AY_BFINE:
- case AY_BCOARSE:
- PSG->Regs[AY_BCOARSE] &= 0x0F;
- old = PSG->PeriodB;
- PSG->PeriodB = (PSG->Regs[AY_BFINE] + 256 * PSG->Regs[AY_BCOARSE]) * PSG->UpdateStep;
-
- if (PSG->PeriodB == 0)
- PSG->PeriodB = PSG->UpdateStep;
-
- PSG->CountB += PSG->PeriodB - old;
-
- if (PSG->CountB <= 0)
- PSG->CountB = 1;
- break;
- case AY_CFINE:
- case AY_CCOARSE:
- PSG->Regs[AY_CCOARSE] &= 0x0F;
- old = PSG->PeriodC;
- PSG->PeriodC = (PSG->Regs[AY_CFINE] + 256 * PSG->Regs[AY_CCOARSE]) * PSG->UpdateStep;
-
- if (PSG->PeriodC == 0)
- PSG->PeriodC = PSG->UpdateStep;
-
- PSG->CountC += PSG->PeriodC - old;
-
- if (PSG->CountC <= 0)
- PSG->CountC = 1;
- break;
- case AY_NOISEPER:
- PSG->Regs[AY_NOISEPER] &= 0x1F;
- old = PSG->PeriodN;
- PSG->PeriodN = PSG->Regs[AY_NOISEPER] * PSG->UpdateStep;
-
- if (PSG->PeriodN == 0)
- PSG->PeriodN = PSG->UpdateStep;
-
- PSG->CountN += PSG->PeriodN - old;
-
- if (PSG->CountN <= 0)
- PSG->CountN = 1;
- break;
-/* case AY_ENABLE:
- if ((PSG->lastEnable == -1) ||
- ((PSG->lastEnable & 0x40) != (PSG->Regs[AY_ENABLE] & 0x40)))
- {
- // write out $FF if port set to input
- if (PSG->PortAwrite)
- (*PSG->PortAwrite)(0, (UINT8) ((PSG->Regs[AY_ENABLE] & 0x40) ? PSG->Regs[AY_PORTA] : 0xff)); // [TC: UINT8 cast]
- }
-
- if ((PSG->lastEnable == -1) ||
- ((PSG->lastEnable & 0x80) != (PSG->Regs[AY_ENABLE] & 0x80)))
- {
- // write out $FF if port set to input
- if (PSG->PortBwrite)
- (*PSG->PortBwrite)(0, (UINT8) ((PSG->Regs[AY_ENABLE] & 0x80) ? PSG->Regs[AY_PORTB] : 0xff)); // [TC: UINT8 cast]
- }
-
- PSG->lastEnable = PSG->Regs[AY_ENABLE];
- break;*/
- case AY_AVOL:
- PSG->Regs[AY_AVOL] &= 0x1F;
- PSG->EnvelopeA = PSG->Regs[AY_AVOL] & 0x10;
- PSG->VolA = (PSG->EnvelopeA ? PSG->VolE :
- (PSG->VolTable[PSG->Regs[AY_AVOL] ? PSG->Regs[AY_AVOL] * 2 + 1
- : 0]));
- break;
- case AY_BVOL:
- PSG->Regs[AY_BVOL] &= 0x1F;
- PSG->EnvelopeB = PSG->Regs[AY_BVOL] & 0x10;
- PSG->VolB = (PSG->EnvelopeB ? PSG->VolE :
- (PSG->VolTable[PSG->Regs[AY_BVOL] ? PSG->Regs[AY_BVOL] * 2 + 1
- : 0]));
- break;
- case AY_CVOL:
- PSG->Regs[AY_CVOL] &= 0x1F;
- PSG->EnvelopeC = PSG->Regs[AY_CVOL] & 0x10;
- PSG->VolC = (PSG->EnvelopeC ? PSG->VolE
- : (PSG->VolTable[PSG->Regs[AY_CVOL] ? PSG->Regs[AY_CVOL] * 2 + 1
- : 0]));
- break;
- case AY_EFINE:
- case AY_ECOARSE:
- old = PSG->PeriodE;
- PSG->PeriodE = ((PSG->Regs[AY_EFINE] + 256 * PSG->Regs[AY_ECOARSE])) * PSG->UpdateStep;
-
- if (PSG->PeriodE == 0)
- PSG->PeriodE = PSG->UpdateStep / 2;
-
- PSG->CountE += PSG->PeriodE - old;
-
- if (PSG->CountE <= 0)
- PSG->CountE = 1;
- break;
- case AY_ESHAPE:
- /* envelope shapes:
- C AtAlH
- 0 0 x x \___
-
- 0 1 x x /___
-
- 1 0 0 0 \\\\
-
- 1 0 0 1 \___
-
- 1 0 1 0 \/\/
- ___
- 1 0 1 1 \
-
- 1 1 0 0 ////
- ___
- 1 1 0 1 /
-
- 1 1 1 0 /\/\
-
- 1 1 1 1 /___
-
- The envelope counter on the AY-3-8910 has 16 steps. On the YM2149 it
- has twice the steps, happening twice as fast. Since the end result is
- just a smoother curve, we always use the YM2149 behaviour.
- */
- PSG->Regs[AY_ESHAPE] &= 0x0F;
- PSG->Attack = (PSG->Regs[AY_ESHAPE] & 0x04 ? 0x1F : 0x00);
-
- if ((PSG->Regs[AY_ESHAPE] & 0x08) == 0)
- {
- /* if Continue = 0, map the shape to the equivalent one which has Continue = 1 */
- PSG->Hold = 1;
- PSG->Alternate = PSG->Attack;
- }
- else
- {
- PSG->Hold = PSG->Regs[AY_ESHAPE] & 0x01;
- PSG->Alternate = PSG->Regs[AY_ESHAPE] & 0x02;
- }
-
- PSG->CountE = PSG->PeriodE;
- PSG->CountEnv = 0x1F;
- PSG->Holding = 0;
- PSG->VolE = PSG->VolTable[PSG->CountEnv ^ PSG->Attack];
-
- if (PSG->EnvelopeA)
- PSG->VolA = PSG->VolE;
-
- if (PSG->EnvelopeB)
- PSG->VolB = PSG->VolE;
-
- if (PSG->EnvelopeC)
- PSG->VolC = PSG->VolE;
- break;
-/* case AY_PORTA:
- if (PSG->Regs[AY_ENABLE] & 0x40)
- {
- if (PSG->PortAwrite)
- (*PSG->PortAwrite)(0, PSG->Regs[AY_PORTA]);
- else
- logerror("PC %04x: warning - write %02x to 8910 #%d Port A\n",activecpu_get_pc(),PSG->Regs[AY_PORTA],n);
- }
- else
- {
- logerror("warning: write to 8910 #%d Port A set as input - ignored\n",n);
- }
- break;
- case AY_PORTB:
- if (PSG->Regs[AY_ENABLE] & 0x80)
- {
- if (PSG->PortBwrite)
- (*PSG->PortBwrite)(0, PSG->Regs[AY_PORTB]);
- else
- logerror("PC %04x: warning - write %02x to 8910 #%d Port B\n",activecpu_get_pc(),PSG->Regs[AY_PORTB],n);
- }
- else
- {
- logerror("warning: write to 8910 #%d Port B set as input - ignored\n",n);
- }
- break;*/
- }
-}
-
-
-//#define DEBUG_AY
-// /length/ is the number of samples we require
-void AY8910Update(int chip, int16_t ** buffer, int length) // [TC: Removed static]
-{
-#ifdef DEBUG_AY
-WriteLog("AY8910Update: chip=%d, buffer=%X, length=%d\n", chip, buffer, length);
-#endif
- struct AY8910 * PSG = &AYPSG[chip];
-
- int16_t * buf1 = buffer[0];
- int16_t * buf2 = buffer[1];
- int16_t * buf3 = buffer[2];
-
- /* The 8910 has three outputs, each output is the mix of one of the three
- * tone generators and of the (single) noise generator. The two are mixed
- * BEFORE going into the DAC. The formula to mix each channel is:
- * (ToneOn | ToneDisable) & (NoiseOn | NoiseDisable).
- * Note that this means that if both tone and noise are disabled, the
- * output is 1, not 0, and can be modulated changing the volume.
- *
- * If the channels are disabled, set their output to 1, and increase the
- * counter, if necessary, so they will not be inverted during this update.
- * Setting the output to 1 is necessary because a disabled channel is
- * locked into the ON state (see above); and it has no effect if the volume
- * is 0. If the volume is 0, increase the counter, but don't touch the
- * output.
- */
- // N.B.: The bits in AY_ENABLE (0-5) are all active LOW, which means if the
- // channel bit is set, it is DISABLED. 5-3 are noise, 2-0 tone.
- if (PSG->Regs[AY_ENABLE] & 0x01)
- {
- if (PSG->CountA <= length * STEP)
- PSG->CountA += length * STEP;
-
- PSG->OutputA = 1;
- }
- else if (PSG->Regs[AY_AVOL] == 0)
- {
- /* note that I do count += length, NOT count = length + 1. You might
- * think it's the same since the volume is 0, but doing the latter
- * could cause interferencies when the program is rapidly modulating
- * the volume.
- */
- if (PSG->CountA <= length * STEP)
- PSG->CountA += length * STEP;
- }
-
- if (PSG->Regs[AY_ENABLE] & 0x02)
- {
- if (PSG->CountB <= length * STEP)
- PSG->CountB += length * STEP;
-
- PSG->OutputB = 1;
- }
- else if (PSG->Regs[AY_BVOL] == 0)
- {
- if (PSG->CountB <= length * STEP)
- PSG->CountB += length * STEP;
- }
-
- if (PSG->Regs[AY_ENABLE] & 0x04)
- {
- if (PSG->CountC <= length * STEP)
- PSG->CountC += length * STEP;
-
- PSG->OutputC = 1;
- }
- else if (PSG->Regs[AY_CVOL] == 0)
- {
- if (PSG->CountC <= length * STEP)
- PSG->CountC += length * STEP;
- }
-
- /* for the noise channel we must not touch OutputN - it's also not
- * necessary since we use outn. */
- if ((PSG->Regs[AY_ENABLE] & 0x38) == 0x38) /* all off */
- if (PSG->CountN <= length * STEP)
- PSG->CountN += length * STEP;
-
- int outn = (PSG->OutputN | PSG->Regs[AY_ENABLE]);
-
-#ifdef DEBUG_AY
-WriteLog("AY8910Update: Stepping into while (length)...\n");
-#endif
- /* buffering loop */
- while (length)
- {
- /* vola, volb and volc keep track of how long each square wave stays
- * in the 1 position during the sample period.
- */
- int vola = 0, volb = 0, volc = 0;
- int left = STEP;
-
-#ifdef DEBUG_AY
-WriteLog("AY8910Update: Stepping into inner do loop... (length=%d)\n", length);
-#endif
- do
- {
- int nextevent = (PSG->CountN < left ? PSG->CountN : left);
-//Note: nextevent is 0 here when first initialized...
-//so let's try this:
- if (nextevent == 0)
- left = 0;
-#ifdef DEBUG_AY
-WriteLog("AY8910Update: nextevent=$%X, left=$%X\n", nextevent, left);
-#endif
-
- if (outn & 0x08)
- {
- if (PSG->OutputA)
- vola += PSG->CountA;
-
- PSG->CountA -= nextevent;
- /* PeriodA is the half period of the square wave. Here, in each
- * loop I add PeriodA twice, so that at the end of the loop the
- * square wave is in the same status (0 or 1) it was at the
- * start. vola is also incremented by PeriodA, since the wave
- * has been 1 exactly half of the time, regardless of the
- * initial position. If we exit the loop in the middle, OutputA
- * has to be inverted and vola incremented only if the exit
- * status of the square wave is 1. */
- while (PSG->CountA <= 0)
- {
- PSG->CountA += PSG->PeriodA;
-
- if (PSG->CountA > 0)
- {
- PSG->OutputA ^= 1;
-
- if (PSG->OutputA)
- vola += PSG->PeriodA;
-
- break;
- }
-
- PSG->CountA += PSG->PeriodA;
- vola += PSG->PeriodA;
- }
-
- if (PSG->OutputA)
- vola -= PSG->CountA;
- }
- else
- {
- PSG->CountA -= nextevent;
-
- while (PSG->CountA <= 0)
- {
- PSG->CountA += PSG->PeriodA;
-
- if (PSG->CountA > 0)
- {
- PSG->OutputA ^= 1;
- break;
- }
-
- PSG->CountA += PSG->PeriodA;
- }
- }
-
- if (outn & 0x10)
- {
- if (PSG->OutputB)
- volb += PSG->CountB;
-
- PSG->CountB -= nextevent;
-
- while (PSG->CountB <= 0)
- {
- PSG->CountB += PSG->PeriodB;
-
- if (PSG->CountB > 0)
- {
- PSG->OutputB ^= 1;
-
- if (PSG->OutputB)
- volb += PSG->PeriodB;
- break;
- }
-
- PSG->CountB += PSG->PeriodB;
- volb += PSG->PeriodB;
- }
-
- if (PSG->OutputB)
- volb -= PSG->CountB;
- }
- else
- {
- PSG->CountB -= nextevent;
-
- while (PSG->CountB <= 0)
- {
- PSG->CountB += PSG->PeriodB;
-
- if (PSG->CountB > 0)
- {
- PSG->OutputB ^= 1;
- break;
- }
-
- PSG->CountB += PSG->PeriodB;
- }
- }
-
- if (outn & 0x20)
- {
- if (PSG->OutputC)
- volc += PSG->CountC;
-
- PSG->CountC -= nextevent;
-
- while (PSG->CountC <= 0)
- {
- PSG->CountC += PSG->PeriodC;
-
- if (PSG->CountC > 0)
- {
- PSG->OutputC ^= 1;
-
- if (PSG->OutputC)
- volc += PSG->PeriodC;
- break;
- }
-
- PSG->CountC += PSG->PeriodC;
- volc += PSG->PeriodC;
- }
-
- if (PSG->OutputC)
- volc -= PSG->CountC;
- }
- else
- {
- PSG->CountC -= nextevent;
-
- while (PSG->CountC <= 0)
- {
- PSG->CountC += PSG->PeriodC;
-
- if (PSG->CountC > 0)
- {
- PSG->OutputC ^= 1;
- break;
- }
-
- PSG->CountC += PSG->PeriodC;
- }
- }
-
- PSG->CountN -= nextevent;
-
- if (PSG->CountN <= 0)
- {
- /* Is noise output going to change? */
- if ((PSG->RNG + 1) & 0x00002) // (bit0 XOR bit1) == 1?
- {
- PSG->OutputN = ~PSG->OutputN;
- outn = (PSG->OutputN | PSG->Regs[AY_ENABLE]);
- }
-
- /* The Random Number Generator of the 8910 is a 17-bit shift
- * register. The input to the shift register is bit0 XOR bit3
- * (bit0 is the output). This was verified on AY-3-8910 and
- * YM2149 chips.
- *
- * The following is a fast way to compute bit17 = bit0^bit3.
- * Instead of doing all the logic operations, we only check
- * bit0, relying on the fact that after three shifts of the
- * register, what now is bit3 will become bit0, and will
- * invert, if necessary, bit14, which previously was bit17. */
- if (PSG->RNG & 0x00001)
- PSG->RNG ^= 0x24000; /* This version is called the "Galois configuration". */
-
- PSG->RNG >>= 1;
- PSG->CountN += PSG->PeriodN;
- }
-
- left -= nextevent;
- }
- while (left > 0);
-
-#ifdef DEBUG_AY
-WriteLog("AY8910Update: About to update envelope...\n");
-#endif
- /* update envelope */
- if (PSG->Holding == 0)
- {
- PSG->CountE -= STEP;
-
- if (PSG->CountE <= 0)
- {
-#ifdef DEBUG_AY
-WriteLog("AY8910Update: About to enter do loop... (CountEnv = $%X, CountE =$%X, PeriodE = $%X)\n", PSG->CountEnv, PSG->CountE, PSG->PeriodE);
-#endif
- // JLH: Sanity check...
- if (PSG->PeriodE > 0)
- {
- do
- {
- PSG->CountEnv--;
- PSG->CountE += PSG->PeriodE;
- }
- while (PSG->CountE <= 0);
- }
-
- /* check envelope current position */
- if (PSG->CountEnv < 0)
- {
- if (PSG->Hold)
- {
- if (PSG->Alternate)
- PSG->Attack ^= 0x1F;
-
- PSG->Holding = 1;
- PSG->CountEnv = 0;
- }
- else
- {
- /* if CountEnv has looped an odd number of times
- * (usually 1), invert the output. */
- if (PSG->Alternate && (PSG->CountEnv & 0x20))
- PSG->Attack ^= 0x1F;
-
- PSG->CountEnv &= 0x1F;
- }
- }
-
- PSG->VolE = PSG->VolTable[PSG->CountEnv ^ PSG->Attack];
-
- /* reload volume */
- if (PSG->EnvelopeA)
- PSG->VolA = PSG->VolE;
-
- if (PSG->EnvelopeB)
- PSG->VolB = PSG->VolE;
-
- if (PSG->EnvelopeC)
- PSG->VolC = PSG->VolE;
- }
- }
-
-#if 1
- *(buf1++) = (vola * PSG->VolA) / STEP;
- *(buf2++) = (volb * PSG->VolB) / STEP;
- *(buf3++) = (volc * PSG->VolC) / STEP;
-#else // [Tom's code...]
- // Output PCM wave [-32768...32767] instead of MAME's voltage level [0...32767]
- // - This allows for better s/w mixing
-
- if (PSG->VolA)
- {
- if (vola)
- *(buf1++) = (vola * PSG->VolA) / STEP;
- else
- *(buf1++) = -(int)PSG->VolA;
- }
- else
- *(buf1++) = 0;
-
- if (PSG->VolB)
- {
- if (volb)
- *(buf2++) = (volb * PSG->VolB) / STEP;
- else
- *(buf2++) = -(int)PSG->VolB;
- }
- else
- *(buf2++) = 0;
-
- if (PSG->VolC)
- {
- if (volc)
- *(buf3++) = (volc * PSG->VolC) / STEP;
- else
- *(buf3++) = -(int)PSG->VolC;
- }
- else
- *(buf3++) = 0;
-#endif
- length--;
- }
-#ifdef DEBUG_AY
-WriteLog("AY8910Update: Done.\n");
-#endif
-}
-
-
-static void AY8910_set_clock(int chip, int clock)
-{
-// struct AY8910 * PSG = &AYPSG[chip];
-
- /* The step clock for the tone and noise generators is the chip clock
- * divided by 8; for the envelope generator of the AY-3-8910, it is half
- * that much (clock/16), but the envelope of the YM2149 goes twice as
- * fast, therefore again clock/8.
- * Here we calculate the number of steps which happen during one sample
- * at the given sample rate. No. of events = sample rate / (clock/8).
- * STEP is a multiplier used to turn the fraction into a fixed point
- * number.
- */
- AYPSG[chip].UpdateStep = (unsigned int)(((double)STEP * AYPSG[chip].SampleRate * 8 + clock / 2) / clock); // [TC: unsigned int cast]
-}
-
-
-static void build_mixer_table(int chip)
-{
- /* calculate the volume->voltage conversion table
- * The AY-3-8910 has 16 levels, in a logarithmic scale (3dB per step)
- * The YM2149 still has 16 levels for the tone generators, but 32 for
- * the envelope generator (1.5dB per step).
- */
- double out = MAX_OUTPUT;
-
- for(int i=31; i>0; i--)
- {
- AYPSG[chip].VolTable[i] = (unsigned int)(out + 0.5); /* round to nearest */ // [TC: unsigned int cast]
- out /= 1.188502227; /* = 10 ^ (1.5/20) = 1.5dB */
- }
-
- AYPSG[chip].VolTable[0] = 0;
-}
-
-
-void AY8910_reset(int chip)
-{
- AYPSG[chip].register_latch = 0;
- AYPSG[chip].RNG = 1;
- AYPSG[chip].OutputA = 0;
- AYPSG[chip].OutputB = 0;
- AYPSG[chip].OutputC = 0;
- AYPSG[chip].OutputN = 0xFF;
-
- for(int i=0; i<=AY_ESHAPE; i++)
- _AYWriteReg(chip, i, 0); /* AYWriteReg() uses the timer system; we
- * cannot call it at this time because the
- * timer system has not been initialized. */
-}
-
-// This stuff looks like Tom's code, so let's streamline and un-MSHungarianize this shit:
-// [DONE]
-// N.B.: Looks like 'clock' is the 65C02 clock rate, and 'sampleRate' is the
-// sample rate set by the audio subsystem.
-
-void AY8910_InitAll(int clock, int sampleRate)
-{
- for(int chip=0; chip<MAX_8910; chip++)
- {
- memset(&AYPSG[chip], 0, sizeof(struct AY8910));
- AYPSG[chip].SampleRate = sampleRate;
- AY8910_set_clock(chip, clock);
- build_mixer_table(chip);
- }
-}
-
-
-void AY8910_InitClock(int clock)
-{
- for(int chip=0; chip<MAX_8910; chip++)
- AY8910_set_clock(chip, clock);
-}
-#endif
-
projects / apple2 / blobdiff