| 1 | /***************************************************************************\r |
| 2 | \r |
| 3 | sn76496.c\r |
| 4 | \r |
| 5 | Routines to emulate the Texas Instruments SN76489 / SN76496 programmable\r |
| 6 | tone /noise generator. Also known as (or at least compatible with) TMS9919.\r |
| 7 | \r |
| 8 | Noise emulation is not accurate due to lack of documentation. The noise\r |
| 9 | generator uses a shift register with a XOR-feedback network, but the exact\r |
| 10 | layout is unknown. It can be set for either period or white noise; again,\r |
| 11 | the details are unknown.\r |
| 12 | \r |
| 13 | 28/03/2005 : Sebastien Chevalier\r |
| 14 | Update th SN76496Write func, according to SN76489 doc found on SMSPower.\r |
| 15 | - On write with 0x80 set to 0, when LastRegister is other then TONE,\r |
| 16 | the function is similar than update with 0x80 set to 1\r |
| 17 | ***************************************************************************/\r |
| 18 | \r |
| 19 | #ifndef __GNUC__\r |
| 20 | #pragma warning (disable:4244)\r |
| 21 | #endif\r |
| 22 | \r |
| 23 | #include "sn76496.h"\r |
| 24 | \r |
| 25 | #define MAX_OUTPUT 0x47ff // was 0x7fff\r |
| 26 | \r |
| 27 | #define STEP 0x10000\r |
| 28 | \r |
| 29 | \r |
| 30 | /* Formulas for noise generator */\r |
| 31 | /* bit0 = output */\r |
| 32 | \r |
| 33 | /* noise feedback for white noise mode (verified on real SN76489 by John Kortink) */\r |
| 34 | #define FB_WNOISE 0x14002 /* (16bits) bit16 = bit0(out) ^ bit2 ^ bit15 */\r |
| 35 | \r |
| 36 | /* noise feedback for periodic noise mode */\r |
| 37 | //#define FB_PNOISE 0x10000 /* 16bit rorate */\r |
| 38 | #define FB_PNOISE 0x08000 /* JH 981127 - fixes Do Run Run */\r |
| 39 | \r |
| 40 | /*\r |
| 41 | 0x08000 is definitely wrong. The Master System conversion of Marble Madness\r |
| 42 | uses periodic noise as a baseline. With a 15-bit rotate, the bassline is\r |
| 43 | out of tune.\r |
| 44 | The 16-bit rotate has been confirmed against a real PAL Sega Master System 2.\r |
| 45 | Hope that helps the System E stuff, more news on the PSG as and when!\r |
| 46 | */\r |
| 47 | \r |
| 48 | /* noise generator start preset (for periodic noise) */\r |
| 49 | #define NG_PRESET 0x0f35\r |
| 50 | \r |
| 51 | \r |
| 52 | struct SN76496\r |
| 53 | {\r |
| 54 | //sound_stream * Channel;\r |
| 55 | int SampleRate;\r |
| 56 | unsigned int UpdateStep;\r |
| 57 | int VolTable[16]; /* volume table */\r |
| 58 | int Register[8]; /* registers */\r |
| 59 | int LastRegister; /* last register written */\r |
| 60 | int Volume[4]; /* volume of voice 0-2 and noise */\r |
| 61 | unsigned int RNG; /* noise generator */\r |
| 62 | int NoiseFB; /* noise feedback mask */\r |
| 63 | int Period[4];\r |
| 64 | int Count[4];\r |
| 65 | int Output[4];\r |
| 66 | int pad[1];\r |
| 67 | };\r |
| 68 | \r |
| 69 | static struct SN76496 ono_sn; // one and only SN76496\r |
| 70 | int *sn76496_regs;\r |
| 71 | \r |
| 72 | //static\r |
| 73 | void SN76496Write(int data)\r |
| 74 | {\r |
| 75 | struct SN76496 *R = &ono_sn;\r |
| 76 | int n, r, c;\r |
| 77 | \r |
| 78 | /* update the output buffer before changing the registers */\r |
| 79 | //stream_update(R->Channel,0);\r |
| 80 | \r |
| 81 | r = R->LastRegister;\r |
| 82 | if (data & 0x80)\r |
| 83 | r = R->LastRegister = (data & 0x70) >> 4;\r |
| 84 | c = r / 2;\r |
| 85 | \r |
| 86 | if (!(data & 0x80) && (r == 0 || r == 2 || r == 4))\r |
| 87 | // data byte (tone only)\r |
| 88 | R->Register[r] = (R->Register[r] & 0x0f) | ((data & 0x3f) << 4);\r |
| 89 | else\r |
| 90 | R->Register[r] = (R->Register[r] & 0x3f0) | (data & 0x0f);\r |
| 91 | \r |
| 92 | data = R->Register[r];\r |
| 93 | switch (r)\r |
| 94 | {\r |
| 95 | case 0: /* tone 0 : frequency */\r |
| 96 | case 2: /* tone 1 : frequency */\r |
| 97 | case 4: /* tone 2 : frequency */\r |
| 98 | R->Period[c] = R->UpdateStep * data;\r |
| 99 | if (R->Period[c] == 0) R->Period[c] = R->UpdateStep;\r |
| 100 | if (r == 4)\r |
| 101 | {\r |
| 102 | /* update noise shift frequency */\r |
| 103 | if ((R->Register[6] & 0x03) == 0x03)\r |
| 104 | R->Period[3] = 2 * R->Period[2];\r |
| 105 | }\r |
| 106 | break;\r |
| 107 | case 1: /* tone 0 : volume */\r |
| 108 | case 3: /* tone 1 : volume */\r |
| 109 | case 5: /* tone 2 : volume */\r |
| 110 | case 7: /* noise : volume */\r |
| 111 | R->Volume[c] = R->VolTable[data & 0x0f];\r |
| 112 | break;\r |
| 113 | case 6: /* noise : frequency, mode */\r |
| 114 | n = data;\r |
| 115 | R->NoiseFB = (n & 4) ? FB_WNOISE : FB_PNOISE;\r |
| 116 | n &= 3;\r |
| 117 | /* N/512,N/1024,N/2048,Tone #3 output */\r |
| 118 | R->Period[3] = (n == 3) ? 2 * R->Period[2] : (R->UpdateStep << (5 + n));\r |
| 119 | \r |
| 120 | /* reset noise shifter */\r |
| 121 | R->RNG = NG_PRESET;\r |
| 122 | R->Output[3] = R->RNG & 1;\r |
| 123 | break;\r |
| 124 | }\r |
| 125 | }\r |
| 126 | \r |
| 127 | /*\r |
| 128 | WRITE8_HANDLER( SN76496_0_w ) { SN76496Write(0,data); }\r |
| 129 | WRITE8_HANDLER( SN76496_1_w ) { SN76496Write(1,data); }\r |
| 130 | WRITE8_HANDLER( SN76496_2_w ) { SN76496Write(2,data); }\r |
| 131 | WRITE8_HANDLER( SN76496_3_w ) { SN76496Write(3,data); }\r |
| 132 | WRITE8_HANDLER( SN76496_4_w ) { SN76496Write(4,data); }\r |
| 133 | */\r |
| 134 | \r |
| 135 | //static\r |
| 136 | void SN76496Update(short *buffer, int length, int stereo)\r |
| 137 | {\r |
| 138 | int i;\r |
| 139 | struct SN76496 *R = &ono_sn;\r |
| 140 | \r |
| 141 | /* If the volume is 0, increase the counter */\r |
| 142 | for (i = 0;i < 4;i++)\r |
| 143 | {\r |
| 144 | if (R->Volume[i] == 0)\r |
| 145 | {\r |
| 146 | /* note that I do count += length, NOT count = length + 1. You might think */\r |
| 147 | /* it's the same since the volume is 0, but doing the latter could cause */\r |
| 148 | /* interferencies when the program is rapidly modulating the volume. */\r |
| 149 | if (R->Count[i] <= length*STEP) R->Count[i] += length*STEP;\r |
| 150 | }\r |
| 151 | }\r |
| 152 | \r |
| 153 | while (length > 0)\r |
| 154 | {\r |
| 155 | int vol[4];\r |
| 156 | unsigned int out;\r |
| 157 | int left;\r |
| 158 | \r |
| 159 | \r |
| 160 | /* vol[] keeps track of how long each square wave stays */\r |
| 161 | /* in the 1 position during the sample period. */\r |
| 162 | vol[0] = vol[1] = vol[2] = vol[3] = 0;\r |
| 163 | \r |
| 164 | for (i = 0;i < 3;i++)\r |
| 165 | {\r |
| 166 | if (R->Output[i]) vol[i] += R->Count[i];\r |
| 167 | R->Count[i] -= STEP;\r |
| 168 | /* Period[i] is the half period of the square wave. Here, in each */\r |
| 169 | /* loop I add Period[i] twice, so that at the end of the loop the */\r |
| 170 | /* square wave is in the same status (0 or 1) it was at the start. */\r |
| 171 | /* vol[i] is also incremented by Period[i], since the wave has been 1 */\r |
| 172 | /* exactly half of the time, regardless of the initial position. */\r |
| 173 | /* If we exit the loop in the middle, Output[i] has to be inverted */\r |
| 174 | /* and vol[i] incremented only if the exit status of the square */\r |
| 175 | /* wave is 1. */\r |
| 176 | while (R->Count[i] <= 0)\r |
| 177 | {\r |
| 178 | R->Count[i] += R->Period[i];\r |
| 179 | if (R->Count[i] > 0)\r |
| 180 | {\r |
| 181 | R->Output[i] ^= 1;\r |
| 182 | if (R->Output[i]) vol[i] += R->Period[i];\r |
| 183 | break;\r |
| 184 | }\r |
| 185 | R->Count[i] += R->Period[i];\r |
| 186 | vol[i] += R->Period[i];\r |
| 187 | }\r |
| 188 | if (R->Output[i]) vol[i] -= R->Count[i];\r |
| 189 | }\r |
| 190 | \r |
| 191 | left = STEP;\r |
| 192 | do\r |
| 193 | {\r |
| 194 | int nextevent;\r |
| 195 | \r |
| 196 | if (R->Count[3] < left) nextevent = R->Count[3];\r |
| 197 | else nextevent = left;\r |
| 198 | \r |
| 199 | if (R->Output[3]) vol[3] += R->Count[3];\r |
| 200 | R->Count[3] -= nextevent;\r |
| 201 | if (R->Count[3] <= 0)\r |
| 202 | {\r |
| 203 | if (R->RNG & 1) R->RNG ^= R->NoiseFB;\r |
| 204 | R->RNG >>= 1;\r |
| 205 | R->Output[3] = R->RNG & 1;\r |
| 206 | R->Count[3] += R->Period[3];\r |
| 207 | if (R->Output[3]) vol[3] += R->Period[3];\r |
| 208 | }\r |
| 209 | if (R->Output[3]) vol[3] -= R->Count[3];\r |
| 210 | \r |
| 211 | left -= nextevent;\r |
| 212 | } while (left > 0);\r |
| 213 | \r |
| 214 | out = vol[0] * R->Volume[0] + vol[1] * R->Volume[1] +\r |
| 215 | vol[2] * R->Volume[2] + vol[3] * R->Volume[3];\r |
| 216 | \r |
| 217 | if (out > MAX_OUTPUT * STEP) out = MAX_OUTPUT * STEP;\r |
| 218 | \r |
| 219 | if ((out /= STEP)) // will be optimized to shift; max 0x47ff = 18431\r |
| 220 | *buffer += out;\r |
| 221 | if(stereo) buffer+=2; // only left for stereo, to be mixed to right later\r |
| 222 | else buffer++;\r |
| 223 | \r |
| 224 | length--;\r |
| 225 | }\r |
| 226 | }\r |
| 227 | \r |
| 228 | \r |
| 229 | static void SN76496_set_clock(struct SN76496 *R,int clock)\r |
| 230 | {\r |
| 231 | \r |
| 232 | /* the base clock for the tone generators is the chip clock divided by 16; */\r |
| 233 | /* for the noise generator, it is clock / 256. */\r |
| 234 | /* Here we calculate the number of steps which happen during one sample */\r |
| 235 | /* at the given sample rate. No. of events = sample rate / (clock/16). */\r |
| 236 | /* STEP is a multiplier used to turn the fraction into a fixed point */\r |
| 237 | /* number. */\r |
| 238 | R->UpdateStep = ((double)STEP * R->SampleRate * 16) / clock;\r |
| 239 | }\r |
| 240 | \r |
| 241 | \r |
| 242 | static void SN76496_set_gain(struct SN76496 *R,int gain)\r |
| 243 | {\r |
| 244 | int i;\r |
| 245 | double out;\r |
| 246 | \r |
| 247 | \r |
| 248 | gain &= 0xff;\r |
| 249 | \r |
| 250 | /* increase max output basing on gain (0.2 dB per step) */\r |
| 251 | out = MAX_OUTPUT / 3;\r |
| 252 | while (gain-- > 0)\r |
| 253 | out *= 1.023292992; /* = (10 ^ (0.2/20)) */\r |
| 254 | \r |
| 255 | /* build volume table (2dB per step) */\r |
| 256 | for (i = 0;i < 15;i++)\r |
| 257 | {\r |
| 258 | /* limit volume to avoid clipping */\r |
| 259 | if (out > MAX_OUTPUT / 3) R->VolTable[i] = MAX_OUTPUT / 3;\r |
| 260 | else R->VolTable[i] = out;\r |
| 261 | \r |
| 262 | out /= 1.258925412; /* = 10 ^ (2/20) = 2dB */\r |
| 263 | }\r |
| 264 | R->VolTable[15] = 0;\r |
| 265 | }\r |
| 266 | \r |
| 267 | \r |
| 268 | //static\r |
| 269 | int SN76496_init(int clock,int sample_rate)\r |
| 270 | {\r |
| 271 | struct SN76496 *R = &ono_sn;\r |
| 272 | int i;\r |
| 273 | \r |
| 274 | //R->Channel = stream_create(0,1, sample_rate,R,SN76496Update);\r |
| 275 | sn76496_regs = R->Register;\r |
| 276 | \r |
| 277 | R->SampleRate = sample_rate;\r |
| 278 | SN76496_set_clock(R,clock);\r |
| 279 | \r |
| 280 | for (i = 0;i < 4;i++) R->Volume[i] = 0;\r |
| 281 | \r |
| 282 | R->LastRegister = 0;\r |
| 283 | for (i = 0;i < 8;i+=2)\r |
| 284 | {\r |
| 285 | R->Register[i] = 0;\r |
| 286 | R->Register[i + 1] = 0x0f; /* volume = 0 */\r |
| 287 | }\r |
| 288 | \r |
| 289 | for (i = 0;i < 4;i++)\r |
| 290 | {\r |
| 291 | R->Output[i] = 0;\r |
| 292 | R->Period[i] = R->Count[i] = R->UpdateStep;\r |
| 293 | }\r |
| 294 | R->RNG = NG_PRESET;\r |
| 295 | R->Output[3] = R->RNG & 1;\r |
| 296 | \r |
| 297 | // added\r |
| 298 | SN76496_set_gain(R, 0);\r |
| 299 | \r |
| 300 | return 0;\r |
| 301 | }\r |
| 302 | \r |