ref: 03eeebb97f014c29a4dd25d873fc6ad50da48f15
parent: f1d29a9d12fa6d89015735ea010ac4b02f1b80b5
author: Michael Forney <mforney@mforney.org>
date: Wed Feb 17 06:20:05 EST 2021
games/snes: implement DSP echo
--- a/sys/src/games/snes/dsp.c
+++ b/sys/src/games/snes/dsp.c
@@ -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,
@@ -24,8 +26,8 @@
EFB = 0x0d,
MVOLR = 0x1c,
EVOLL = 0x2c,
- EVOLR = 0x2d,
PMON = 0x2d,
+ EVOLR = 0x3c,
NON = 0x3d,
EON = 0x4d,
KON = 0x4c,
@@ -32,7 +34,9 @@
KOFF = 0x5c,
DIR = 0x5d,
FLG = 0x6c,
+ ESA = 0x6d,
ENDX = 0x7c,
+ EDL = 0x7d,
NEWKON = 0x8e,
INT = 0x80,
};
@@ -96,6 +100,13 @@
return v;
}
+static void
+spcput16(u16int p, u16int v)
+{+ spcmem[p++] = v;
+ spcmem[p] = v >> 8;
+}
+
u8int
dspread(u8int p)
{@@ -412,33 +423,57 @@
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 @@
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;
}
}