/* * Copyright (C) 2002-2004 The DOSBox Team * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Library General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ /* Based of sn76496.c of the M.A.M.E. project */ #include #include "dosbox.h" #include "inout.h" #include "mixer.h" #include "mem.h" #include "setup.h" #include "pic.h" #define MAX_OUTPUT 0x7fff #define STEP 0x10000 /* Formulas for noise generator */ /* bit0 = output */ /* noise feedback for white noise mode (verified on real SN76489 by John Kortink) */ #define FB_WNOISE 0x14002 /* (16bits) bit16 = bit0(out) ^ bit2 ^ bit15 */ /* noise feedback for periodic noise mode */ //#define FB_PNOISE 0x10000 /* 16bit rorate */ #define FB_PNOISE 0x08000 /* JH 981127 - fixes Do Run Run */ /* 0x08000 is definitely wrong. The Master System conversion of Marble Madness uses periodic noise as a baseline. With a 15-bit rotate, the bassline is out of tune. The 16-bit rotate has been confirmed against a real PAL Sega Master System 2. Hope that helps the System E stuff, more news on the PSG as and when! */ /* noise generator start preset (for periodic noise) */ #define NG_PRESET 0x0f35 struct SN76496 { int SampleRate; unsigned int UpdateStep; int VolTable[16]; /* volume table */ int Register[8]; /* registers */ int LastRegister; /* last register written */ int Volume[4]; /* volume of voice 0-2 and noise */ unsigned int RNG; /* noise generator */ int NoiseFB; /* noise feedback mask */ int Period[4]; int Count[4]; int Output[4]; }; static struct SN76496 sn; static struct { MIXER_Channel * chan; bool enabled; Bitu last_write; } tandy; static void SN76496Write(Bit32u port,Bit8u data) { struct SN76496 *R = &sn; tandy.last_write=PIC_Ticks; if (!tandy.enabled) { MIXER_Enable(tandy.chan,true); tandy.enabled=true; } /* update the output buffer before changing the registers */ if (data & 0x80) { int r = (data & 0x70) >> 4; int c = r/2; R->LastRegister = r; R->Register[r] = (R->Register[r] & 0x3f0) | (data & 0x0f); switch (r) { case 0: /* tone 0 : frequency */ case 2: /* tone 1 : frequency */ case 4: /* tone 2 : frequency */ R->Period[c] = R->UpdateStep * R->Register[r]; if (R->Period[c] == 0) R->Period[c] = R->UpdateStep; if (r == 4) { /* update noise shift frequency */ if ((R->Register[6] & 0x03) == 0x03) R->Period[3] = 2 * R->Period[2]; } break; case 1: /* tone 0 : volume */ case 3: /* tone 1 : volume */ case 5: /* tone 2 : volume */ case 7: /* noise : volume */ R->Volume[c] = R->VolTable[data & 0x0f]; break; case 6: /* noise : frequency, mode */ { int n = R->Register[6]; R->NoiseFB = (n & 4) ? FB_WNOISE : FB_PNOISE; n &= 3; /* N/512,N/1024,N/2048,Tone #3 output */ R->Period[3] = (n == 3) ? 2 * R->Period[2] : (R->UpdateStep << (5+n)); /* reset noise shifter */ R->RNG = NG_PRESET; R->Output[3] = R->RNG & 1; } break; } } else { int r = R->LastRegister; int c = r/2; switch (r) { case 0: /* tone 0 : frequency */ case 2: /* tone 1 : frequency */ case 4: /* tone 2 : frequency */ R->Register[r] = (R->Register[r] & 0x0f) | ((data & 0x3f) << 4); R->Period[c] = R->UpdateStep * R->Register[r]; if (R->Period[c] == 0) R->Period[c] = R->UpdateStep; if (r == 4) { /* update noise shift frequency */ if ((R->Register[6] & 0x03) == 0x03) R->Period[3] = 2 * R->Period[2]; } break; } } } static void SN76496Update(Bit8u * stream,Bit32u length) { if ((tandy.last_write+1000)Volume[i] == 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 (R->Count[i] <= (int)length*STEP) R->Count[i] += length*STEP; } } while (length > 0) { int vol[4]; unsigned int out; int left; /* vol[] keeps track of how long each square wave stays */ /* in the 1 position during the sample period. */ vol[0] = vol[1] = vol[2] = vol[3] = 0; for (i = 0;i < 3;i++) { if (R->Output[i]) vol[i] += R->Count[i]; R->Count[i] -= STEP; /* Period[i] is the half period of the square wave. Here, in each */ /* loop I add Period[i] 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. */ /* vol[i] is also incremented by Period[i], since the wave has been 1 */ /* exactly half of the time, regardless of the initial position. */ /* If we exit the loop in the middle, Output[i] has to be inverted */ /* and vol[i] incremented only if the exit status of the square */ /* wave is 1. */ while (R->Count[i] <= 0) { R->Count[i] += R->Period[i]; if (R->Count[i] > 0) { R->Output[i] ^= 1; if (R->Output[i]) vol[i] += R->Period[i]; break; } R->Count[i] += R->Period[i]; vol[i] += R->Period[i]; } if (R->Output[i]) vol[i] -= R->Count[i]; } left = STEP; do { int nextevent; if (R->Count[3] < left) nextevent = R->Count[3]; else nextevent = left; if (R->Output[3]) vol[3] += R->Count[3]; R->Count[3] -= nextevent; if (R->Count[3] <= 0) { if (R->RNG & 1) R->RNG ^= R->NoiseFB; R->RNG >>= 1; R->Output[3] = R->RNG & 1; R->Count[3] += R->Period[3]; if (R->Output[3]) vol[3] += R->Period[3]; } if (R->Output[3]) vol[3] -= R->Count[3]; left -= nextevent; } while (left > 0); out = vol[0] * R->Volume[0] + vol[1] * R->Volume[1] + vol[2] * R->Volume[2] + vol[3] * R->Volume[3]; if (out > MAX_OUTPUT * STEP) out = MAX_OUTPUT * STEP; *(buffer++) = out / STEP; length--; } } static void SN76496_set_clock(int clock) { struct SN76496 *R = &sn; /* the base clock for the tone generators is the chip clock divided by 16; */ /* for the noise generator, it is clock / 256. */ /* Here we calculate the number of steps which happen during one sample */ /* at the given sample rate. No. of events = sample rate / (clock/16). */ /* STEP is a multiplier used to turn the fraction into a fixed point */ /* number. */ R->UpdateStep = (unsigned int)(((double)STEP * R->SampleRate * 16) / clock); } static void SN76496_set_gain(int gain) { struct SN76496 *R = &sn; int i; double out; gain &= 0xff; /* increase max output basing on gain (0.2 dB per step) */ out = MAX_OUTPUT / 3; while (gain-- > 0) out *= 1.023292992; /* = (10 ^ (0.2/20)) */ /* build volume table (2dB per step) */ for (i = 0;i < 15;i++) { /* limit volume to avoid clipping */ if (out > MAX_OUTPUT / 3) R->VolTable[i] = MAX_OUTPUT / 3; else R->VolTable[i] = (int)out; out /= 1.258925412; /* = 10 ^ (2/20) = 2dB */ } R->VolTable[15] = 0; } void TANDYSOUND_Init(Section* sec) { Section_prop * section=static_cast(sec); if(!section->Get_bool("tandy")) return; IO_RegisterWriteHandler(0xc0,SN76496Write,"Tandy Sound"); Bit32u sample_rate = section->Get_int("tandyrate"); tandy.chan=MIXER_AddChannel(&SN76496Update,sample_rate,"TANDY"); MIXER_Enable(tandy.chan,false); tandy.enabled=false; MIXER_SetMode(tandy.chan,MIXER_16MONO); Bitu i; struct SN76496 *R = &sn; R->SampleRate = sample_rate; SN76496_set_clock(2386360); for (i = 0;i < 4;i++) R->Volume[i] = 0; R->LastRegister = 0; for (i = 0;i < 8;i+=2) { R->Register[i] = 0; R->Register[i + 1] = 0x0f; /* volume = 0 */ } for (i = 0;i < 4;i++) { R->Output[i] = 0; R->Period[i] = R->Count[i] = R->UpdateStep; } R->RNG = NG_PRESET; R->Output[3] = R->RNG & 1; SN76496_set_gain(0x1); }