sys/src/games/c64/mem.c

   1 #include <u.h>
   2 #include <libc.h>
   3 #include <thread.h>
   4 #include "dat.h"
   5 #include "fns.h"
   6
   7 u8int pla;
   8 u8int ram[65536], krom[8192], brom[8192], crom[4096], cart[16384], cram[1024];
   9 u8int reg[47];
  10 u16int vicbank;
  11 u8int cia[32];
  12 u16int timer[4], timrel[4];
  13
  14 enum {
  15         TIMEREN = 1,
  16         TIMERUND = 2,
  17         TIMERSTOP = 8,
  18         TIMERASRC = 0x20,
  19         TIMERBSRC = 0x60,
  20         TIMERBSYS = 0,
  21         TIMERBA = 0x40,
  22 };
  23
  24 u8int
  25 ciaread(int n, u8int a)
  26 {
  27         u8int r;
  28         int i;
  29
  30         switch(a){
  31         case 0:
  32                 return (cia[0] | ~cia[2]) & (~joys >> 5 | 0xe0);
  33         case 1:
  34                 if(!n){
  35                         r = 0;
  36                         for(i = 0; i < 8; i++)
  37                                 if((cia[0] & 1<<i) == 0)
  38                                         r |= keys >> 8 * i;
  39                         return (cia[1] | ~cia[3]) & ~r & (~joys | 0xe0);
  40                 }
  41                 break;
  42         case 4: return timer[n*2];
  43         case 5: return timer[n*2] >> 8;
  44         case 6: return timer[n*2+1];
  45         case 7: return timer[n*2+1] >> 8;
  46         case 13:
  47                 if(n){
  48                         r = nmi >> 4 & 0x1f | ((nmi & nmien & 0x1f0) != 0) << 7;
  49                         nmi &= ~0x1f0;
  50                         return r;
  51                 }else{
  52                         r = irq >> 4 & 0x1f | ((irq & irqen & 0x1f0) != 0) << 7;
  53                         irq &= ~0x1f0;
  54                         return r;
  55                 }
  56         }
  57         return cia[n * 16 + a];
  58 }
  59
  60 void
  61 ciawrite(int n, u8int a, u8int v)
  62 {
  63         switch(a){
  64         case 0:
  65                 if(n)
  66                         vicbank = (~v & 3) << 14;
  67                 break;
  68         case 4: timrel[n*2] = v | timrel[n*2] & 0xff00; break;
  69         case 5: timrel[n*2] = v << 8 | timrel[n*2] & 0xff; break;
  70         case 6: timrel[n*2+1] = v | timrel[n*2+1] & 0xff00; break;
  71         case 7: timrel[n*2+1] = v << 8 | timrel[n*2+1] & 0xff; break;
  72         case 13:
  73                 if(n)
  74                         if((v & 0x80) != 0)
  75                                 nmien |= v << 4 & 0x1f0;
  76                         else
  77                                 nmien &= ~(v << 4 & 0x1f0);
  78                 else
  79                         if((v & 0x80) != 0)
  80                                 irqen |= v << 4 & 0x1f0;
  81                         else
  82                                 irqen &= ~(v << 4 & 0x1f0);
  83                 break;
  84         case 14: case 15:
  85                 if((v & 0x10) != 0){
  86                         timer[n * 2 + (a & 1)] = timrel[n * 2 + (a & 1)];
  87                         v &= ~0x10;
  88                 }
  89                 break;
  90         }
  91         cia[n * 16 + a] = v;
  92 }
  93
  94 u8int
  95 mioread(u16int a)
  96 {
  97         u8int b, v;
  98
  99         switch(a & 0xc00){
 100         case 0:
 101                 b = a & 63;
 102                 switch(b){
 103                 case CTRL1:
 104                         return reg[b] & 0x7f | ppuy >> 1 & 0x80;
 105                 case RASTER:
 106                         return ppuy;
 107                 case IRQLATCH:
 108                         return irq & 0xf | (irq & irqen & 0xf) + 0x7f & 0x80;
 109                 case IRQEN:
 110                         return irqen & 0xf;
 111                 case SPRSPR:
 112                 case SPRBG:
 113                         v = reg[b];
 114                         reg[b] = 0;
 115                         return v;
 116                 }
 117                 if(b >= 0x20)
 118                         return reg[b] | 0xf0;
 119                 if(b >= 47)
 120                         return 0xff;
 121                 return reg[b];
 122         case 0x800:
 123                 return cram[a & 0x3ff];
 124         case 0xc00:
 125                 if((a & 0x200) == 0)
 126                         return ciaread(a >> 8 & 1, a & 0xf);
 127         default:
 128                 return 0xff;
 129         }
 130 }
 131
 132 void
 133 miowrite(u16int a, u8int v)
 134 {
 135         u8int b;
 136
 137         switch(a & 0xc00){
 138         case 0:
 139                 b = a & 63;
 140                 if(b >= 0x20)
 141                         v &= 0xf;
 142                 switch(b){
 143                 case CTRL2: v |= 0xc0; break;
 144                 case IRQLATCH:
 145                         v |= 0xf0;
 146                         irq &= ~(v & 0xf);
 147                         break;
 148                 case IRQEN:
 149                         irqen = irqen & ~0xf | v & 0xf;
 150                         v |= 0xf0;
 151                         break;
 152                 }
 153                 if(b < 47)
 154                         reg[b] = v;
 155                 if(b == CTRL1 || b == CTRL2)
 156                         bordset();
 157                 return;
 158         case 0x800:
 159                 cram[a & 0x3ff] = v & 0xf;
 160                 return;
 161         case 0xc00:
 162                 if((a & 0x200) == 0)
 163                         ciawrite(a >> 8 & 1, a & 0xf, v);
 164                 return;
 165         }
 166 }
 167
 168 void
 169 tapestep(void)
 170 {
 171         static int tapectr;
 172         static int idx;
 173
 174         if((ram[1] & 1<<5) != 0)
 175                 return;
 176         if(tapectr == 0){
 177                 if(idx >= tapelen){
 178                         progress(0, 0);
 179                         tapeplay = 0;
 180                         idx = 0;
 181                         return;
 182                 }
 183                 tapectr = tape[idx++] << 3;
 184                 if(tapever == 1 && tapectr == 0){
 185                         tapectr = tape[idx++];
 186                         tapectr |= tape[idx++] << 8;
 187                         tapectr |= tape[idx++] << 16;
 188                 }
 189                 progress(idx, tapelen);
 190         }else{
 191                 tapectr--;
 192                 if(tapectr == 0)
 193                         irq |= IRQFLAG;
 194         }
 195 }
 196
 197 void
 198 timerstep(void)
 199 {
 200         int i, at;
 201         u8int a, b;
 202         u16int *t;
 203
 204         for(i = 0; i < 2; i++){
 205                 a = cia[i * 16 + 14];
 206                 b = cia[i * 16 + 15];
 207                 at = 0;
 208                 t = &timer[2 * i];
 209                 if((a & (TIMEREN|TIMERASRC)) == TIMEREN){
 210                         t[0]--;
 211                         if(t[0] == 0){
 212                                 at = 1;
 213                                 if(i)
 214                                         nmi |= IRQTIMERA;
 215                                 else
 216                                         irq |= IRQTIMERA;
 217                                 if((a & TIMERSTOP) != 0)
 218                                         cia[i * 16 + 14] &= ~TIMEREN;
 219                                 t[0] = timrel[2 * i];
 220                         }
 221                 }
 222                 if((b & TIMEREN) != 0 && ((b & TIMERBSRC) == TIMERBSYS || (b & TIMERBSRC) == TIMERBA && at)){
 223                         t[1]--;
 224                         if(t[1] == 0){
 225                                 if(i)
 226                                         nmi |= IRQTIMERB;
 227                                 else
 228                                         irq |= IRQTIMERB;
 229                                 if((b & TIMERSTOP) == 0)
 230                                         cia[i * 16 + 15] &= ~TIMEREN;
 231                                 t[1] = timrel[2 * i + 1];
 232                         }
 233                 }
 234         }
 235         if(tapeplay)
 236                 tapestep();
 237 }
 238
 239 void
 240 io(void)
 241 {
 242         vicstep();
 243         timerstep();
 244 }
 245
 246 u8int
 247 memread(u16int a)
 248 {
 249         io();
 250         if(a == 1)
 251                 return ram[1] & ~(1<<4) | (tapeplay ^ 1) << 4;
 252         switch(a >> 12){
 253         case 8: case 9:
 254                 if((pla & (EXROM|GAME)) == EXROM || (pla & (EXROM|HIRAM|LORAM)) == (HIRAM|LORAM))
 255                         return cart[a & 0x1fff];
 256                 goto def;
 257         case 10: case 11:
 258                 if((pla & (GAME|HIRAM|LORAM)) == (GAME|HIRAM|LORAM))
 259                         return brom[a & 0x1fff];
 260                 if((pla & (EXROM|GAME|HIRAM)) == HIRAM)
 261                         return cart[8192 + (a & 0x1fff)];
 262                 goto def;
 263         case 13:
 264                 if((pla & (HIRAM|LORAM)) == 0 || pla == 1)
 265                         goto def;
 266                 if((pla & CHAREN) == 0 && (pla & (EXROM|GAME)) != EXROM)
 267                         return crom[a & 0xfff];
 268                 return mioread(a & 0xfff);
 269         case 14: case 15:
 270                 if((pla & (EXROM|GAME)) == EXROM)
 271                         return cart[8192 + (a & 0x1fff)];
 272                 if((pla & HIRAM) == HIRAM)
 273                         return krom[a & 0x1fff];
 274         def:
 275         default:
 276                 return ram[a];
 277         }
 278 }
 279
 280 void
 281 memwrite(u16int a, u8int v)
 282 {
 283         if(a >> 12 == 13 && !((pla & (HIRAM|LORAM)) == 0 || pla == 1 || (pla & CHAREN) == 0 && (pla & (EXROM|GAME)) != EXROM))
 284                 miowrite(a & 0xfff, v);
 285         ram[a] = v;
 286         if(a == 1)
 287                 pla = pla & ~7 | v & 7;
 288         io();
 289 }
 290
 291 u8int
 292 vmemread(u16int a)
 293 {
 294         a |= vicbank;
 295         if((a & 0x7000) == 0x1000)
 296                 return crom[a & 0xfff];
 297         return ram[a];
 298 }
 299
 300 void
 301 memreset(void)
 302 {
 303         pla = 0x1f;
 304 }