ref: 974c4fc768c12af947af13de75c227ef7e6ca50d
dir: /sys/src/games/nes/mem.c/
#include <u.h>
#include <libc.h>
#include <thread.h>
#include <draw.h>
#include "dat.h"
#include "fns.h"
uchar mem[32768];
uchar ppuram[16384];
uchar oam[256];
uchar *prgb[16], *chrb[16];
u16int pput, ppuv;
u8int ppusx, vrambuf;
int vramlatch = 1, keylatch = 0xFF, keylatch2 = 0xFF;
int prgsh, chrsh, mmc3hack;
static void
nope(int p)
{
print("unimplemented mapper function %d (mapper %d)\n", p, map);
}
static void
nrom(int p, u8int)
{
if(p >= 0)
return;
switch(p){
case INIT:
case RSTR:
prgb[0] = prg;
if(nprg == 1)
prgb[1] = prg;
else
prgb[1] = prg + 0x4000;
prgsh = 14;
chrb[0] = chr;
chrsh = 13;
break;
case SAVE:
case SCAN:
break;
default:
nope(p);
}
}
static void
mmc1(int v, u8int p)
{
static u8int n, s, mode, c0, c1, pr;
static int mirrs[] = {MSINGB, MSINGA, MVERT, MHORZ};
if(v < 0){
switch(v){
case INIT:
if(nprg > 32)
sysfatal("bad rom, too much prg rom for mmc1");
mode = 0x0C;
prgsh = 14;
chrsh = 12;
goto t;
case RSTR:
mode = get8();
c0 = get8();
c1 = get8();
pr = get8();
n = get8();
s = get8();
goto t;
case SAVE:
put8(mode);
put8(c0);
put8(c1);
put8(pr);
put8(n);
put8(s);
break;
default:
nope(v);
case SCAN:
break;
}
return;
}
if((p & 0x80) != 0){
n = 0;
s = 0;
mode |= 0xC;
return;
}
s |= (p & 1) << 4;
if(n < 4){
n++;
s >>= 1;
return;
}
switch(v & 0xE000){
case 0x8000:
mode = s;
mirr = mirrs[mode & 3];
break;
case 0xA000:
if(nprg > 16){
pr = s & 0x10 | pr & 0x0f;
pr %= nprg;
}
c0 = s & 0x1f;
c0 %= 2*nchr;
break;
case 0xC000:
c1 = s & 0x1f;
c1 %= 2*nchr;
break;
case 0xE000:
pr = pr & 0x10 | s & 0x0f;
pr %= nprg;
break;
}
s = 0;
n = 0;
t:
switch(mode & 0x0c){
case 0x08:
prgb[0] = prg;
prgb[1] = prg + pr * 0x4000;
break;
case 0x0C:
prgb[0] = prg + pr * 0x4000;
prgb[1] = prg + ((pr & 0x10 | 0x0f) % nprg) * 0x4000;
break;
default:
prgb[0] = prg + (pr & 0xfe) * 0x4000;
prgb[1] = prg + (pr | 1) * 0x4000;
break;
}
if((mode & 0x10) != 0){
chrb[0] = chr + c0 * 0x1000;
chrb[1] = chr + c1 * 0x1000;
}else{
chrb[0] = chr + (c0 & 0xfe) * 0x1000;
chrb[1] = chr + (c0 | 1) * 0x1000;
}
}
static void
uxrom(int p, u8int v)
{
static u8int b;
if(p < 0)
switch(p){
case INIT:
prgsh = 14;
chrsh = 13;
prgb[1] = prg + (nprg - 1) * 0x4000;
chrb[0] = chr;
break;
case SAVE:
put8(b);
return;
case RSTR:
b = get8();
break;
case SCAN:
return;
default:
nope(p);
return;
}
else
b = v % nprg;
prgb[0] = prg + b * 0x4000;
}
static void
cnrom(int p, u8int v)
{
static u8int b;
if(p < 0)
switch(p){
case INIT:
prgsh = 14;
chrsh = 13;
prgb[0] = prg;
if(nprg == 1)
prgb[1] = prg;
else
prgb[1] = prg + 0x4000;
break;
case SAVE:
put8(b);
return;
case RSTR:
b = get8();
break;
case SCAN:
return;
default:
nope(p);
return;
}
else
b = v % nchr;
chrb[0] = chr + b * 0x2000;
}
static void
mmc3(int p, u8int v)
{
static u8int m, b[8], l, n, en;
int i, j, c;
if(p < 0){
switch(p){
case INIT:
prgsh = 13;
chrsh = 10;
mmc3hack = 1;
prgb[2] = prg + (2 * nprg - 2) * 0x2000;
prgb[3] = prgb[2] + 0x2000;
goto t;
case SCAN:
if(n == 0)
n = l;
else
n--;
if(n == 0 && en)
irq |= IRQMMC;
return;
case SAVE:
put8(m);
for(i = 0; i < 8; i++)
put8(b[i]);
put8(l);
put8(n);
put8(en);
return;
case RSTR:
m = get8();
for(i = 0; i < 8; i++)
b[i] = get8();
l = get8();
n = get8();
en = get8();
goto t;
}
}
switch(p & 0xE001){
case 0x8000:
if(((m ^ v) & 0xc0) != 0){
m = v;
goto t;
}
m = v;
break;
case 0x8001:
i = m & 7;
if(i < 6)
v %= 8 * nchr;
else
v %= 2 * nprg;
b[i] = v;
goto t;
case 0xA000:
if(mirr == MFOUR)
break;
if(v & 1)
mirr = MHORZ;
else
mirr = MVERT;
break;
case 0xC000: l = v; break;
case 0xC001: n = 0; break;
case 0xE000: en = 0; irq &= ~IRQMMC; break;
case 0xE001: en = 1; break;
}
return;
t:
if((m & 0x40) != 0){
prgb[0] = prg + (2 * nprg - 2) * 0x2000;
prgb[2] = prg + b[6] * 0x2000;
}else{
prgb[0] = prg + b[6] * 0x2000;
prgb[2] = prg + (2 * nprg - 2) * 0x2000;
}
prgb[1] = prg + b[7] * 0x2000;
c = (m & 0x80) >> 5;
for(i = 0; i < 2; i++){
chrb[j = (i << 1) ^ c] = chr + (b[i] >> 1) * 0x800;
chrb[j+1] = chrb[j] + 0x400;
}
for(i = 2; i < 6; i++)
chrb[(i + 2) ^ c] = chr + b[i] * 0x400;
}
static void
axrom(int p, u8int v)
{
static int b;
if(p >= 0)
b = v;
else
switch(p){
case INIT:
nrom(INIT, 0);
b = 0;
break;
case SAVE:
put8(b);
return;
case RSTR:
b = get8();
break;
case SCAN:
return;
default:
nope(p);
return;
}
prgb[0] = prg + (b & 3) * 0x8000;
prgb[1] = prgb[0] + 0x4000;
}
void (*mapper[256])(int, u8int) = {
[0] nrom,
[1] mmc1,
[2] uxrom,
[3] cnrom,
[4] mmc3,
[7] axrom,
};
static void
incvram(void)
{
int old;
old = ppuv;
if((mem[PPUCTRL] & VRAMINC) != 0)
ppuv += 32;
else
ppuv += 1;
ppuv &= 0x3FFF;
if(mmc3hack && (old & (1<<12)) == 0 && (ppuv & (1<<12)) != 0)
mapper[map](SCAN, 0);
}
u8int
memread(u16int p)
{
u8int v;
int i;
if(p < 0x2000){
p &= 0x7FF;
}else if(p < 0x6000){
if(p < 0x4000)
p &= 0x2007;
switch(p){
case 0x2002:
v = mem[p];
mem[p] &= ~PPUVBLANK;
vramlatch = 1;
return v;
case 0x2004:
return oam[mem[0x2003]];
case 0x2007:
if(ppuv < 0x4000){
v = vrambuf;
vrambuf = ppuread(ppuv);
incvram();
return v;
}
vrambuf = ppuread(ppuv);
incvram();
return vrambuf;
case APUSTATUS:
v = (irq & 3) << 6;
for(i = 0; i < 4; i++){
if(apuctr[i] != 0)
v |= (1<<i);
}
if(mem[0x4013] != 0)
v |= (1<<4);
irq &= ~IRQFRAME;
return v;
case 0x4016:
if((mem[p] & 1) != 0)
return keys & 1;
v = keylatch & 1;
keylatch = (keylatch >> 1) | 0x80;
return v | 0x40;
case 0x4017:
if((mem[p] & 1) != 0)
return keys2 & 1;
v = keylatch2 & 1;
keylatch2 = (keylatch2 >> 1) | 0x80;
return v | 0x40;
}
}
if(p >= 0x8000){
p -= 0x8000;
return prgb[p >> prgsh][p & ((1 << prgsh) - 1)];
}
return mem[p];
}
void
memwrite(u16int p, u8int v)
{
extern u8int apulen[32];
extern u16int dmclen[16];
int i;
if(p < 0x2000){
p &= 0x7FF;
}else if(p < 0x6000){
if(p < 0x4000)
p &= 0x2007;
switch(p){
case PPUCTRL:
if((mem[PPUCTRL] & PPUNMI) == 0 && (v & PPUNMI) != 0 &&
(mem[PPUSTATUS] & PPUVBLANK) != 0)
nmi = 1;
pput = (pput & 0xF3FF) | ((v & 3) << 10);
break;
case PPUSTATUS:
return;
case 0x2004:
oam[mem[0x2003]++] = v;
return;
case 0x2005:
if(vramlatch){
ppusx = v & 7;
pput = (pput & 0xFFE0) | (v >> 3);
}else
pput = (pput & 0x0C1F) | ((v & 0xF8) << 2) | ((v & 7) << 12);
vramlatch ^= 1;
return;
case 0x2006:
if(vramlatch)
pput = (pput & 0xFF) | (v << 8) & 0x3F00;
else{
pput = (pput & 0xFF00) | v;
if(mmc3hack && (ppuv & (1<<12)) == 0 && (pput & (1<<12)) != 0)
mapper[map](SCAN, 0);
ppuv = pput;
}
vramlatch ^= 1;
return;
case 0x2007:
ppuwrite(ppuv, v);
incvram();
return;
case 0x4001:
case 0x4005:
i = (p & 0xC) >> 2;
apuctr[i+8] |= 0x80;
break;
case 0x4003:
case 0x4007:
case 0x400B:
case 0x400F:
i = (p & 0xC) >> 2;
if((mem[APUSTATUS] & (1<<i)) != 0){
apuctr[i] = apulen[v >> 3];
apuctr[10] |= (1<<i);
}
break;
case DMCCTRL:
if((v & 0x80) == 0)
irq &= ~IRQDMC;
dmcfreq = 12 * dmclen[v & 0xf];
break;
case DMCBUF:
v &= ~0x80;
break;
case 0x4014:
memcpy(oam, mem + (v<<8), sizeof(oam));
return;
case APUSTATUS:
for(i = 0; i < 4; i++)
if((v & (1<<i)) == 0)
apuctr[i] = 0;
if((v & 0x10) != 0 && dmccnt == 0){
dmcaddr = mem[DMCADDR] * 0x40 + 0xC000;
dmccnt = mem[DMCLEN] * 0x10 + 1;
}
irq &= ~IRQDMC;
break;
case 0x4016:
if((mem[p] & 1) != 0 && (v & 1) == 0){
keylatch = keys;
keylatch2 = keys2;
}
break;
case APUFRAME:
apuseq = 0;
if((v & 0x80) != 0)
apuclock = APUDIV;
else
apuclock = 0;
if((v & 0x40) != 0)
irq &= ~IRQFRAME;
break;
}
}else if(p < 0x8000){
if(saveclock == 0)
saveclock = SAVEFREQ;
}else{
if(mapper[map] != nil)
mapper[map](p, v);
return;
}
mem[p] = v;
}
static uchar *
ppumap(u16int p)
{
if(p >= 0x3F00){
if((p & 3) == 0)
p &= 0x3F0F;
return ppuram + (p & 0x3F1F);
}
p &= 0x3FFF;
if(p >= 0x3000)
p &= 0x2FFF;
if(p >= 0x2000)
switch(mirr){
case MHORZ: if((p & 0x800) != 0) p |= 0x400; else p &= ~0x400; break;
case MVERT: if((p & 0x400) != 0) p |= 0x800; else p &= ~0x800; break;
case MSINGA: p &= ~0xC00; break;
case MSINGB: p |= 0xC00; break;
}
if(p < 0x2000)
return chrb[p >> chrsh] + (p & ((1 << chrsh) - 1));
else
return ppuram + p;
}
u8int
ppuread(u16int p)
{
return *ppumap(p);
}
void
ppuwrite(u16int p, u8int v)
{
*ppumap(p) = v;
}