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games/nes: bug fixing

--- a/sys/src/games/nes/cpu.c

+++ b/sys/src/games/nes/cpu.c

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

 u16int pc, curpc;

 u8int rA, rX, rY, rS, rP;

 int nmi;

+extern int map;

 static u8int

 fetch8(void)

@@ -172,7 +173,13 @@

 static void

 inc(u16int a)

 {

-	memwrite(a, nz(memread(a) + 1));

+	u8int v;

+

+	v = memread(a);

+	memwrite(a, v);

+	v = nz(v + 1);

+	if(!(map == 1 && a >= 0x8000))

+		memwrite(a, v);

 }

 static void

@@ -229,6 +236,8 @@

 	rP |= FLAGI;

 }

+int trace;

+

 int

 step(void)

 {

@@ -243,6 +252,8 @@

 	}

 	curpc = pc;

 	op = fetch8();

+	if(trace)

+		print("%x %x %x %x %x %x %x %x\n", curpc, op, rA, rX, rY, rS, rP, memread(0x2c));

 	switch(op){

 	case 0x00: pc++; interrupt(0, 1); return 7;

 	case 0x01: nz(rA |= indX()); return 6;

@@ -397,12 +408,12 @@

 	case 0xC5: cmp(rA, zp()); return 3;

 	case 0xC9: cmp(rA, imm()); return 2;

 	case 0xCD: cmp(rA, abso()); return 4;

+	case 0xD0: if((rP & FLAGZ) == 0) return branch(); pc++; return 3;

 	case 0xD1: cmp(rA, indY(&c)); return 5 + c;

 	case 0xD5: cmp(rA, zpX()); return 4;

 	case 0xD8: rP &= ~FLAGD; return 2;

 	case 0xD9: cmp(rA, absY()); return 4 + ((u8int)a < rY);

 	case 0xDD: cmp(rA, absX()); return 4 + ((u8int)a < rX);

-	case 0xD0: if((rP & FLAGZ) == 0) return branch(); pc++; return 3;

 	case 0xC0: cmp(rY, imm()); return 2;

 	case 0xC4: cmp(rY, zp()); return 3;

 	case 0xC6: dec(fetch8()); return 5;

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

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

@@ -193,7 +193,8 @@

 			p &= 0x2007;

 		switch(p){

 		case PPUCTRL:

-			if((v & PPUNMI) != 0 && (mem[PPUSTATUS] & PPUVBLANK) != 0)

+			if((mem[PPUCTRL] & PPUNMI) == 0 && (v & PPUNMI) != 0 &&

+			   (mem[PPUSTATUS] & PPUVBLANK) != 0)

 				nmi = 1;

 			pput = (pput & 0xF3FF) | ((v & 3) << 10);

 			break;

--- a/sys/src/games/nes/nes.c

+++ b/sys/src/games/nes/nes.c

@@ -83,6 +83,8 @@

 	mapper[map](-1, 0);

 }

+extern int trace;

+

 void

 keyproc(void *)

 {

@@ -99,6 +101,8 @@

 		if(buf[0] == 'c'){

 			if(utfrune(buf, Kdel))

 				threadexitsall(nil);

+			if(utfrune(buf, 't'))

+				trace ^= 1;

 		}

 		if(buf[0] != 'k' && buf[0] != 'K')

 			continue;

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

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

@@ -5,7 +5,7 @@

 #include "dat.h"

 #include "fns.h"

-int ppuy, ppux;

+int ppuy, ppux, odd;

 uchar pic[256*240*4*9];

 extern uchar oam[256];

@@ -289,7 +289,11 @@

 	if(ppux > 340){

 		ppux = 0;

 		ppuy++;

-		if(ppuy > 261)

+		if(ppuy > 261){

 			ppuy = 0;

+			if(odd && (mem[PPUCTRL] & (BGDISP | SPRITEDISP)) != 0)

+				ppux++;

+			odd ^= 1;

+		}

 	}

 }