sys/src/games/c64/mem.c

   1 #include <u.h>
   2 #include <libc.h>
   3 #include <thread.h>
   4 #include <emu.h>
   5 #include "dat.h"
   6 #include "fns.h"
   7
   8 u8int pla;
   9 u8int ram[65536], krom[8192], brom[8192], crom[4096], cart[16384], cram[1024];
  10 u8int reg[47];
  11 u16int vicbank;
  12 u8int cia[32];
  13 u16int timer[4], timrel[4];
  14
  15 enum {
  16         TIMEREN = 1,
  17         TIMERUND = 2,
  18         TIMERSTOP = 8,
  19         TIMERASRC = 0x20,
  20         TIMERBSRC = 0x60,
  21         TIMERBSYS = 0,
  22         TIMERBA = 0x40,
  23 };
  24
  25 u8int
  26 ciaread(int n, u8int a)
  27 {
  28         u8int r;
  29         int i;
  30
  31         switch(a){
  32         case 0:
  33                 return (cia[0] | ~cia[2]) & (~joys >> 5 | 0xe0);
  34         case 1:
  35                 if(!n){
  36                         r = 0;
  37                         for(i = 0; i < 8; i++)
  38                                 if((cia[0] & 1<<i) == 0)
  39                                         r |= keys >> 8 * i;
  40                         return (cia[1] | ~cia[3]) & ~r & (~joys | 0xe0);
  41                 }
  42                 break;
  43         case 4: return timer[n*2];
  44         case 5: return timer[n*2] >> 8;
  45         case 6: return timer[n*2+1];
  46         case 7: return timer[n*2+1] >> 8;
  47         case 13:
  48                 if(n){
  49                         r = nmi >> 4 & 0x1f | ((nmi & nmien & 0x1f0) != 0) << 7;
  50                         nmi &= ~0x1f0;
  51                         return r;
  52                 }else{
  53                         r = irq >> 4 & 0x1f | ((irq & irqen & 0x1f0) != 0) << 7;
  54                         irq &= ~0x1f0;
  55                         return r;
  56                 }
  57         }
  58         return cia[n * 16 + a];
  59 }
  60
  61 void
  62 ciawrite(int n, u8int a, u8int v)
  63 {
  64         switch(a){
  65         case 0:
  66                 if(n)
  67                         vicbank = (~v & 3) << 14;
  68                 break;
  69         case 4: timrel[n*2] = v | timrel[n*2] & 0xff00; break;
  70         case 5: timrel[n*2] = v << 8 | timrel[n*2] & 0xff; break;
  71         case 6: timrel[n*2+1] = v | timrel[n*2+1] & 0xff00; break;
  72         case 7: timrel[n*2+1] = v << 8 | timrel[n*2+1] & 0xff; break;
  73         case 13:
  74                 if(n)
  75                         if((v & 0x80) != 0)
  76                                 nmien |= v << 4 & 0x1f0;
  77                         else
  78                                 nmien &= ~(v << 4 & 0x1f0);
  79                 else
  80                         if((v & 0x80) != 0)
  81                                 irqen |= v << 4 & 0x1f0;
  82                         else
  83                                 irqen &= ~(v << 4 & 0x1f0);
  84                 break;
  85         case 14: case 15:
  86                 if((v & 0x10) != 0){
  87                         timer[n * 2 + (a & 1)] = timrel[n * 2 + (a & 1)];
  88                         v &= ~0x10;
  89                 }
  90                 break;
  91         }
  92         cia[n * 16 + a] = v;
  93 }
  94
  95 u8int
  96 mioread(u16int a)
  97 {
  98         u8int b, v;
  99
 100         switch(a & 0xc00){
 101         case 0:
 102                 b = a & 63;
 103                 switch(b){
 104                 case CTRL1:
 105                         return reg[b] & 0x7f | ppuy >> 1 & 0x80;
 106                 case RASTER:
 107                         return ppuy;
 108                 case IRQLATCH:
 109                         return irq & 0xf | (irq & irqen & 0xf) + 0x7f & 0x80;
 110                 case IRQEN:
 111                         return irqen & 0xf;
 112                 case SPRSPR:
 113                 case SPRBG:
 114                         v = reg[b];
 115                         reg[b] = 0;
 116                         return v;
 117                 }
 118                 if(b >= 0x20)
 119                         return reg[b] | 0xf0;
 120                 if(b >= 47)
 121                         return 0xff;
 122                 return reg[b];
 123         case 0x800:
 124                 return cram[a & 0x3ff];
 125         case 0xc00:
 126                 if((a & 0x200) == 0)
 127                         return ciaread(a >> 8 & 1, a & 0xf);
 128         default:
 129                 return 0xff;
 130         }
 131 }
 132
 133 void
 134 miowrite(u16int a, u8int v)
 135 {
 136         u8int b;
 137
 138         switch(a & 0xc00){
 139         case 0:
 140                 b = a & 63;
 141                 if(b >= 0x20)
 142                         v &= 0xf;
 143                 switch(b){
 144                 case CTRL2: v |= 0xc0; break;
 145                 case IRQLATCH:
 146                         v |= 0xf0;
 147                         irq &= ~(v & 0xf);
 148                         break;
 149                 case IRQEN:
 150                         irqen = irqen & ~0xf | v & 0xf;
 151                         v |= 0xf0;
 152                         break;
 153                 }
 154                 if(b < 47)
 155                         reg[b] = v;
 156                 if(b == CTRL1 || b == CTRL2)
 157                         bordset();
 158                 return;
 159         case 0x800:
 160                 cram[a & 0x3ff] = v & 0xf;
 161                 return;
 162         case 0xc00:
 163                 if((a & 0x200) == 0)
 164                         ciawrite(a >> 8 & 1, a & 0xf, v);
 165                 return;
 166         }
 167 }
 168
 169 void
 170 tapestep(void)
 171 {
 172         static int tapectr;
 173         static int idx;
 174
 175         if((ram[1] & 1<<5) != 0)
 176                 return;
 177         if(tapectr == 0){
 178                 if(idx >= tapelen){
 179                         progress(0, 0);
 180                         tapeplay = 0;
 181                         idx = 0;
 182                         return;
 183                 }
 184                 tapectr = tape[idx++] << 3;
 185                 if(tapever == 1 && tapectr == 0){
 186                         tapectr = tape[idx++];
 187                         tapectr |= tape[idx++] << 8;
 188                         tapectr |= tape[idx++] << 16;
 189                 }
 190                 progress(idx, tapelen);
 191         }else{
 192                 tapectr--;
 193                 if(tapectr == 0)
 194                         irq |= IRQFLAG;
 195         }
 196 }
 197
 198 void
 199 timerstep(void)
 200 {
 201         int i, at;
 202         u8int a, b;
 203         u16int *t;
 204
 205         for(i = 0; i < 2; i++){
 206                 a = cia[i * 16 + 14];
 207                 b = cia[i * 16 + 15];
 208                 at = 0;
 209                 t = &timer[2 * i];
 210                 if((a & (TIMEREN|TIMERASRC)) == TIMEREN){
 211                         t[0]--;
 212                         if(t[0] == 0){
 213                                 at = 1;
 214                                 if(i)
 215                                         nmi |= IRQTIMERA;
 216                                 else
 217                                         irq |= IRQTIMERA;
 218                                 if((a & TIMERSTOP) != 0)
 219                                         cia[i * 16 + 14] &= ~TIMEREN;
 220                                 t[0] = timrel[2 * i];
 221                         }
 222                 }
 223                 if((b & TIMEREN) != 0 && ((b & TIMERBSRC) == TIMERBSYS || (b & TIMERBSRC) == TIMERBA && at)){
 224                         t[1]--;
 225                         if(t[1] == 0){
 226                                 if(i)
 227                                         nmi |= IRQTIMERB;
 228                                 else
 229                                         irq |= IRQTIMERB;
 230                                 if((b & TIMERSTOP) == 0)
 231                                         cia[i * 16 + 15] &= ~TIMEREN;
 232                                 t[1] = timrel[2 * i + 1];
 233                         }
 234                 }
 235         }
 236         if(tapeplay)
 237                 tapestep();
 238 }
 239
 240 void
 241 io(void)
 242 {
 243         vicstep();
 244         timerstep();
 245 }
 246
 247 u8int
 248 memread(u16int a)
 249 {
 250         io();
 251         if(a == 1)
 252                 return ram[1] & ~(1<<4) | (tapeplay ^ 1) << 4;
 253         switch(a >> 12){
 254         case 8: case 9:
 255                 if((pla & (EXROM|GAME)) == EXROM || (pla & (EXROM|HIRAM|LORAM)) == (HIRAM|LORAM))
 256                         return cart[a & 0x1fff];
 257                 goto def;
 258         case 10: case 11:
 259                 if((pla & (GAME|HIRAM|LORAM)) == (GAME|HIRAM|LORAM))
 260                         return brom[a & 0x1fff];
 261                 if((pla & (EXROM|GAME|HIRAM)) == HIRAM)
 262                         return cart[8192 + (a & 0x1fff)];
 263                 goto def;
 264         case 13:
 265                 if((pla & (HIRAM|LORAM)) == 0 || pla == 1)
 266                         goto def;
 267                 if((pla & CHAREN) == 0 && (pla & (EXROM|GAME)) != EXROM)
 268                         return crom[a & 0xfff];
 269                 return mioread(a & 0xfff);
 270         case 14: case 15:
 271                 if((pla & (EXROM|GAME)) == EXROM)
 272                         return cart[8192 + (a & 0x1fff)];
 273                 if((pla & HIRAM) == HIRAM)
 274                         return krom[a & 0x1fff];
 275         def:
 276         default:
 277                 return ram[a];
 278         }
 279 }
 280
 281 void
 282 memwrite(u16int a, u8int v)
 283 {
 284         if(a >> 12 == 13 && !((pla & (HIRAM|LORAM)) == 0 || pla == 1 || (pla & CHAREN) == 0 && (pla & (EXROM|GAME)) != EXROM)){
 285                 miowrite(a & 0xfff, v);
 286                 io();
 287                 return;
 288         }
 289         ram[a] = v;
 290         if(a == 1)
 291                 pla = pla & ~7 | v & 7;
 292         io();
 293 }
 294
 295 u8int
 296 vmemread(u16int a)
 297 {
 298         a |= vicbank;
 299         if((a & 0x7000) == 0x1000)
 300                 return crom[a & 0xfff];
 301         return ram[a];
 302 }
 303
 304 void
 305 memreset(void)
 306 {
 307         pla = 0x1f;
 308 }