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games/snes: implement DSP echo

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This commit is contained in:
Michael Forney 2021-02-17 11:20:05 +01:00
parent f1d29a9d12
commit 03eeebb97f
1 changed files with 62 additions and 14 deletions
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76
sys/src/games/snes/dsp.c
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@ -7,7 +7,9 @@
u8int dsp[256], dspstate;
u16int dspcounter, noise = 0x8000;
static s16int samp[2], echoin[2];
static s16int samp[2], echoin[2], echobuf[2*2*8];
static u16int echoaddr;
static int echobp, echopos;
enum {
VOLL = 0,
@ -24,15 +26,17 @@ enum {
EFB = 0x0d,
MVOLR = 0x1c,
EVOLL = 0x2c,
EVOLR = 0x2d,
PMON = 0x2d,
EVOLR = 0x3c,
NON = 0x3d,
EON = 0x4d,
KON = 0x4c,
KOFF = 0x5c,
DIR = 0x5d,
FLG = 0x6c,
ESA = 0x6d,
ENDX = 0x7c,
EDL = 0x7d,
NEWKON = 0x8e,
INT = 0x80,
};
@ -96,6 +100,13 @@ spc16(u16int p)
return v;
}
static void
spcput16(u16int p, u16int v)
{
spcmem[p++] = v;
spcmem[p] = v >> 8;
}
u8int
dspread(u8int p)
{
@ -412,33 +423,57 @@ static void
echo(int s)
{
static s16int echoout[2];
static u8int fir[8];
s16int *x;
s8int h;
int a, b;
x = echobuf + echobp;
switch(s){
case 22:
echoout[0] = 0;
fir[0] = dsp[0x0f];
echoaddr = (dsp[INT|ESA] << 8) + echopos;
x[0] = x[16] = spc16(echoaddr);
h = dsp[0x0f];
echoout[0] = x[2] * h >> 7;
echoout[1] = x[3] * h >> 7;
break;
case 23:
fir[1] = dsp[0x1f];
fir[2] = dsp[0x2f];
h = dsp[0x1f];
echoout[0] += x[4] * h >> 7;
echoout[1] += x[5] * h >> 7;
h = dsp[0x2f];
echoout[0] += x[6] * h >> 7;
echoout[1] += x[7] * h >> 7;
x[1] = x[17] = spc16(echoaddr + 2);
break;
case 24:
fir[3] = dsp[0x3f];
fir[4] = dsp[0x4f];
fir[5] = dsp[0x5f];
h = dsp[0x3f];
echoout[0] += x[8] * h >> 7;
echoout[1] += x[9] * h >> 7;
h = dsp[0x4f];
echoout[0] += x[10] * h >> 7;
echoout[1] += x[11] * h >> 7;
h = dsp[0x5f];
echoout[0] += x[12] * h >> 7;
echoout[1] += x[13] * h >> 7;
break;
case 25:
fir[6] = dsp[0x6f];
fir[7] = dsp[0x7f];
h = dsp[0x6f];
echoout[0] += x[14] * h >> 7;
echoout[1] += x[15] * h >> 7;
h = dsp[0x7f];
echoout[0] += x[16] * h >> 7;
echoout[1] += x[17] * h >> 7;
echoout[0] &= ~1;
echoout[1] &= ~1;
break;
case 26:
a = (samp[0] * (s8int)dsp[MVOLL]) >> 7;
b = (echoout[0] * (s8int)dsp[EVOLL]) >> 7;
samp[0] = clamp16(a + b);
echoin[0] = (echoin[0] * (s8int)dsp[EFB]) >> 7;
echoin[1] = (echoin[1] * (s8int)dsp[EFB]) >> 7;
a = echoout[0] * (s8int)dsp[EFB] >> 7;
echoin[0] = clamp16(echoin[0] + a) & ~1;
a = echoout[1] * (s8int)dsp[EFB] >> 7;
echoin[1] = clamp16(echoin[1] + a) & ~1;
break;
case 27:
a = (samp[1] * (s8int)dsp[MVOLR]) >> 7;
@ -449,9 +484,22 @@ echo(int s)
dsp[INT|FLG] = dsp[FLG];
break;
case 29:
dsp[INT|ESA] = dsp[ESA];
if(echopos == 0)
dsp[INT|EDL] = dsp[EDL] & 0xf;
echopos += 4;
if(echopos >= dsp[INT|EDL] << 11)
echopos = 0;
if((dsp[INT|FLG] & 0x20) == 0)
spcput16(echoaddr, echoin[0]);
echoin[0] = 0;
dsp[INT|FLG] = dsp[FLG];
break;
case 30:
if((dsp[INT|FLG] & 0x20) == 0)
spcput16(echoaddr + 2, echoin[1]);
echoin[1] = 0;
echobp = echobp + 2 & 15;
break;
}
}