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games/snes: bug fixes

--- a/sys/src/games/snes/mem.c

+++ b/sys/src/games/snes/mem.c

@@ -38,9 +38,19 @@

 }

 static void

+vramread(void)

+{

+	u16int b;

+

+	b = vrammap(reg[0x2116] | reg[0x2117] << 8);

+	vramlatch = vram[b++];

+	vramlatch |= vram[b] << 8;

+}

+

+static void

 incvram(int i, int r)

 {

-	u16int a, b;

+	u16int a;

 	int c;

 	c = reg[0x2115];

@@ -47,11 +57,8 @@

 	if((c >> 7) != i)

 		return;

 	a = reg[0x2116] | reg[0x2117] << 8;

-	if(r){

-		b = vrammap(a);

-		vramlatch = vram[b++];

-		vramlatch |= vram[b] << 8;

-	}

+	if(r)

+		vramread();

 	switch(c & 3){

 	case 0: a++; break;

 	case 1: a += 32; break;

@@ -162,14 +169,14 @@

 			return reg[OPVCTH] | mdr2 & 0xfe;

 		return mdr2 = reg[p];

 	case 0x213e:

-		return (mdr1 = reg[p]) | mdr & 0x10;

+		return mdr1 = reg[p] | mdr1 & 0x10;

 	case 0x213f:

-		v = 2 | reg[OPCTLATCH] & 0x40;

+		v = reg[OPCTLATCH] & 0x40;

 		if((reg[0x4201] & 0x80) != 0)

 			reg[OPCTLATCH] &= ~0x43;

 		else

 			reg[OPCTLATCH] &= ~3;

-		return mdr2 = v | mdr2 & 0x20;

+		return mdr2 = reg[p] | v | mdr2 & 0x20;

 	case 0x2180:

 		v = memread(0x7e0000 | reg[0x2181] | reg[0x2182] << 8 | (reg[0x2183] & 1) << 16);

 		incwram();

@@ -189,7 +196,9 @@

 	case 0x4017:

 		return 0x1f | mdr & 0xe0;

 	case 0x4210:

-		return reg[p] | mdr & 0x70;

+		v = reg[p];

+		reg[p] &= ~VBLANK;

+		return v | mdr & 0x70;

 	case 0x4211:

 		v = irq;

 		irq &= ~IRQPPU;

@@ -209,6 +218,10 @@

 	case 0x4219: case 0x421a: case 0x421b: case 0x421c: case 0x421d:

 	case 0x421e: case 0x421f:

 		return reg[p];

+	case 0x2104: case 0x2105: case 0x2106: case 0x2108: case 0x2109: case 0x210a:

+	case 0x2114: case 0x2115: case 0x2116: case 0x2118: case 0x2119: case 0x211a:

+	case 0x2124: case 0x2125: case 0x2126: case 0x2128: case 0x2129: case 0x212a:

+		return mdr1;

 	}

 	if((p & 0xff80) == 0x4300)

 		return reg[p];

@@ -270,11 +283,12 @@

 		vofs[(p - 0x210e) >> 1] = v << 8 | reg[OFSPREV];

 		reg[OFSPREV] = v;

 		break;

-	case 0x2116:

-		break;

 	case 0x2117:

 		v &= 0x7f;

-		break;

+	case 0x2116:

+		reg[p] = v;

+		vramread();

+		return;

 	case 0x2118:

 		a = vrammap(reg[0x2116] | reg[0x2117] << 8);

 		vram[a] = v;

@@ -620,6 +634,7 @@

 memreset(void)

 {

 	reg[0x213e] = 1;

+	reg[0x213f] = 2;

 	reg[0x4201] = 0xff;

 	reg[0x4210] = 2;

 }

--- a/sys/src/games/snes/ppu.c

+++ b/sys/src/games/snes/ppu.c

@@ -618,7 +618,7 @@

 		u32int *ch;

 	} t[32], *tp;

 	static u32int ch[34];

-	static u8int *p, q, over;

+	static u8int *p, q;

 	static int n, m;

 	static int *sz;

 	static int szs[] = {

@@ -635,7 +635,6 @@

 	if(rx == 0){

 		n = 0;

-		over = 1;

 		sp = s;

 		sz = szs + ((reg[OBSEL] & 0xe0) >> 3);

 		base[0] = (reg[OBSEL] & 0x07) << 14;

@@ -654,10 +653,10 @@

 		sp->x = p[0];

 		if((q & 1) != 0)

 			sp->x |= 0xff00;

-		if(sp->x < -(short)sp->sx && sp->x != -256)

+		if(sp->x <= -(short)sp->sx && sp->x != -256)

 			goto nope;

 		if(n == 32){

-			over |= 0x40;

+			reg[0x213e] |= 0x40;

 			goto nope;

 		}

 		sp->i = rx >> 1;

@@ -742,7 +741,7 @@

 						*cp++ = w;

 						tp->sx += 8;

 					}else

-						over |= 0x80;

+						reg[0x213e] |= 0x80;

 				}

 			}else

 				for(i = 0; i < nt; i++){

@@ -755,7 +754,7 @@

 						tp->sx += 8;

 						a += 15;

 					}else

-						over |= 0x80;

+						reg[0x213e] |= 0x80;

 				}

 			if(sp->x < 0 && (i = (-sp->x) & 7) != 0)

 				if((sp->c & 0x40) != 0)

@@ -763,7 +762,6 @@

 				else

 					*tp->ch <<= i;

 		}

-		reg[0x213e] = over;

 	}

 }

@@ -868,6 +866,8 @@

 		if(++ppuy >= 262){

 			ppuy = 0;

 			reg[RDNMI] &= ~VBLANK;

+			reg[0x213e] = 1;

+			reg[0x213f] ^= 0x80;

 			hdma = reg[0x420c]<<8;

 			flush();

 		}