| 1 |
/** M6502: portable 6502 emulator ****************************/ |
| 2 |
/** **/ |
| 3 |
/** M6502.c **/ |
| 4 |
/** **/ |
| 5 |
/** This file contains implementation for 6502 CPU. Don't **/ |
| 6 |
/** forget to provide Rd6502(), Wr6502(), Loop6502(), and **/ |
| 7 |
/** possibly Op6502() functions to accomodate the emulated **/ |
| 8 |
/** machine's architecture. **/ |
| 9 |
/** **/ |
| 10 |
/** Copyright (C) Marat Fayzullin 1996-2007 **/ |
| 11 |
/** Alex Krasivsky 1996 **/ |
| 12 |
/** You are not allowed to distribute this software **/ |
| 13 |
/** commercially. Please, notify me, if you make any **/ |
| 14 |
/** changes to this file. **/ |
| 15 |
/*************************************************************/ |
| 16 |
|
| 17 |
#include "M6502.h" |
| 18 |
#include "Tables.h" |
| 19 |
#include <stdio.h> |
| 20 |
|
| 21 |
/** INLINE ***************************************************/ |
| 22 |
/** C99 standard has "inline", but older compilers used **/ |
| 23 |
/** __inline for the same purpose. **/ |
| 24 |
/*************************************************************/ |
| 25 |
#ifdef __C99__ |
| 26 |
#define INLINE static inline |
| 27 |
#else |
| 28 |
#define INLINE static __inline |
| 29 |
#endif |
| 30 |
|
| 31 |
/** System-Dependent Stuff ***********************************/ |
| 32 |
/** This is system-dependent code put here to speed things **/ |
| 33 |
/** up. It has to stay inlined to be fast. **/ |
| 34 |
/*************************************************************/ |
| 35 |
#ifdef INES |
| 36 |
#define FAST_RDOP |
| 37 |
extern byte *Page[]; |
| 38 |
INLINE byte Op6502(register word A) |
| 39 |
{ |
| 40 |
#ifndef S60 |
| 41 |
return(Page[A>>13][A&0x1FFF]); |
| 42 |
#else |
| 43 |
asm |
| 44 |
( |
| 45 |
"and r2,%1,#0xE000\t\n" |
| 46 |
"ldr r2,[%2,r2,lsr #11]\t\n" |
| 47 |
"mov %0,%1,lsl #19\t\n" |
| 48 |
"ldrb %0,[r2,%0,lsr #19]\t\n" |
| 49 |
: "=r"(A) |
| 50 |
: "0"(A),"r"(Page) |
| 51 |
: "r2" |
| 52 |
); |
| 53 |
return(A); |
| 54 |
#endif /* S60 */ |
| 55 |
} |
| 56 |
#endif /* INES */ |
| 57 |
|
| 58 |
/** FAST_RDOP ************************************************/ |
| 59 |
/** With this #define not present, Rd6502() should perform **/ |
| 60 |
/** the functions of Rd6502(). **/ |
| 61 |
/*************************************************************/ |
| 62 |
#ifndef FAST_RDOP |
| 63 |
#define Op6502(A) Rd6502(A) |
| 64 |
#endif |
| 65 |
|
| 66 |
/** Addressing Methods ***************************************/ |
| 67 |
/** These macros calculate and return effective addresses. **/ |
| 68 |
/*************************************************************/ |
| 69 |
#define MC_Ab(Rg) M_LDWORD(Rg) |
| 70 |
#define MC_Zp(Rg) Rg.W=Op6502(R->PC.W++) |
| 71 |
#define MC_Zx(Rg) Rg.W=(byte)(Op6502(R->PC.W++)+R->X) |
| 72 |
#define MC_Zy(Rg) Rg.W=(byte)(Op6502(R->PC.W++)+R->Y) |
| 73 |
#define MC_Ax(Rg) M_LDWORD(Rg);Rg.W+=R->X |
| 74 |
#define MC_Ay(Rg) M_LDWORD(Rg);Rg.W+=R->Y |
| 75 |
#define MC_Ix(Rg) K.W=(byte)(Op6502(R->PC.W++)+R->X); \ |
| 76 |
Rg.B.l=Op6502(K.W++);Rg.B.h=Op6502(K.W) |
| 77 |
#define MC_Iy(Rg) K.W=Op6502(R->PC.W++); \ |
| 78 |
Rg.B.l=Op6502(K.W++);Rg.B.h=Op6502(K.W); \ |
| 79 |
Rg.W+=R->Y |
| 80 |
|
| 81 |
/** Reading From Memory **************************************/ |
| 82 |
/** These macros calculate address and read from it. **/ |
| 83 |
/*************************************************************/ |
| 84 |
#define MR_Ab(Rg) MC_Ab(J);Rg=Rd6502(J.W) |
| 85 |
#define MR_Im(Rg) Rg=Op6502(R->PC.W++) |
| 86 |
#define MR_Zp(Rg) MC_Zp(J);Rg=Rd6502(J.W) |
| 87 |
#define MR_Zx(Rg) MC_Zx(J);Rg=Rd6502(J.W) |
| 88 |
#define MR_Zy(Rg) MC_Zy(J);Rg=Rd6502(J.W) |
| 89 |
#define MR_Ax(Rg) MC_Ax(J);Rg=Rd6502(J.W) |
| 90 |
#define MR_Ay(Rg) MC_Ay(J);Rg=Rd6502(J.W) |
| 91 |
#define MR_Ix(Rg) MC_Ix(J);Rg=Rd6502(J.W) |
| 92 |
#define MR_Iy(Rg) MC_Iy(J);Rg=Rd6502(J.W) |
| 93 |
|
| 94 |
/** Writing To Memory ****************************************/ |
| 95 |
/** These macros calculate address and write to it. **/ |
| 96 |
/*************************************************************/ |
| 97 |
#define MW_Ab(Rg) MC_Ab(J);Wr6502(J.W,Rg) |
| 98 |
#define MW_Zp(Rg) MC_Zp(J);Wr6502(J.W,Rg) |
| 99 |
#define MW_Zx(Rg) MC_Zx(J);Wr6502(J.W,Rg) |
| 100 |
#define MW_Zy(Rg) MC_Zy(J);Wr6502(J.W,Rg) |
| 101 |
#define MW_Ax(Rg) MC_Ax(J);Wr6502(J.W,Rg) |
| 102 |
#define MW_Ay(Rg) MC_Ay(J);Wr6502(J.W,Rg) |
| 103 |
#define MW_Ix(Rg) MC_Ix(J);Wr6502(J.W,Rg) |
| 104 |
#define MW_Iy(Rg) MC_Iy(J);Wr6502(J.W,Rg) |
| 105 |
|
| 106 |
/** Modifying Memory *****************************************/ |
| 107 |
/** These macros calculate address and modify it. **/ |
| 108 |
/*************************************************************/ |
| 109 |
#define MM_Ab(Cmd) MC_Ab(J);I=Rd6502(J.W);Cmd(I);Wr6502(J.W,I) |
| 110 |
#define MM_Zp(Cmd) MC_Zp(J);I=Rd6502(J.W);Cmd(I);Wr6502(J.W,I) |
| 111 |
#define MM_Zx(Cmd) MC_Zx(J);I=Rd6502(J.W);Cmd(I);Wr6502(J.W,I) |
| 112 |
#define MM_Ax(Cmd) MC_Ax(J);I=Rd6502(J.W);Cmd(I);Wr6502(J.W,I) |
| 113 |
|
| 114 |
/** Other Macros *********************************************/ |
| 115 |
/** Calculating flags, stack, jumps, arithmetics, etc. **/ |
| 116 |
/*************************************************************/ |
| 117 |
#define M_FL(Rg) R->P=(R->P&~(Z_FLAG|N_FLAG))|ZNTable[Rg] |
| 118 |
#define M_LDWORD(Rg) Rg.B.l=Op6502(R->PC.W++);Rg.B.h=Op6502(R->PC.W++) |
| 119 |
|
| 120 |
#define M_PUSH(Rg) Wr6502(0x0100|R->S,Rg);R->S-- |
| 121 |
#define M_POP(Rg) R->S++;Rg=Op6502(0x0100|R->S) |
| 122 |
#define M_JR R->PC.W+=(offset)Op6502(R->PC.W)+1;R->ICount-- |
| 123 |
|
| 124 |
#ifdef NO_DECIMAL |
| 125 |
|
| 126 |
#define M_ADC(Rg) \ |
| 127 |
K.W=R->A+Rg+(R->P&C_FLAG); \ |
| 128 |
R->P&=~(N_FLAG|V_FLAG|Z_FLAG|C_FLAG); \ |
| 129 |
R->P|=(~(R->A^Rg)&(R->A^K.B.l)&0x80? V_FLAG:0)| \ |
| 130 |
(K.B.h? C_FLAG:0)|ZNTable[K.B.l]; \ |
| 131 |
R->A=K.B.l |
| 132 |
|
| 133 |
/* Warning! C_FLAG is inverted before SBC and after it */ |
| 134 |
#define M_SBC(Rg) \ |
| 135 |
K.W=R->A-Rg-(~R->P&C_FLAG); \ |
| 136 |
R->P&=~(N_FLAG|V_FLAG|Z_FLAG|C_FLAG); \ |
| 137 |
R->P|=((R->A^Rg)&(R->A^K.B.l)&0x80? V_FLAG:0)| \ |
| 138 |
(K.B.h? 0:C_FLAG)|ZNTable[K.B.l]; \ |
| 139 |
R->A=K.B.l |
| 140 |
|
| 141 |
#else /* NO_DECIMAL */ |
| 142 |
|
| 143 |
#define M_ADC(Rg) \ |
| 144 |
if(R->P&D_FLAG) \ |
| 145 |
{ \ |
| 146 |
K.B.l=(R->A&0x0F)+(Rg&0x0F)+(R->P&C_FLAG); \ |
| 147 |
if(K.B.l>9) K.B.l+=6; \ |
| 148 |
K.B.h=(R->A>>4)+(Rg>>4)+(K.B.l>15? 1:0); \ |
| 149 |
R->A=(K.B.l&0x0F)|(K.B.h<<4); \ |
| 150 |
R->P=(R->P&~C_FLAG)|(K.B.h>15? C_FLAG:0); \ |
| 151 |
} \ |
| 152 |
else \ |
| 153 |
{ \ |
| 154 |
K.W=R->A+Rg+(R->P&C_FLAG); \ |
| 155 |
R->P&=~(N_FLAG|V_FLAG|Z_FLAG|C_FLAG); \ |
| 156 |
R->P|=(~(R->A^Rg)&(R->A^K.B.l)&0x80? V_FLAG:0)| \ |
| 157 |
(K.B.h? C_FLAG:0)|ZNTable[K.B.l]; \ |
| 158 |
R->A=K.B.l; \ |
| 159 |
} |
| 160 |
|
| 161 |
/* Warning! C_FLAG is inverted before SBC and after it */ |
| 162 |
#define M_SBC(Rg) \ |
| 163 |
if(R->P&D_FLAG) \ |
| 164 |
{ \ |
| 165 |
K.B.l=(R->A&0x0F)-(Rg&0x0F)-(~R->P&C_FLAG); \ |
| 166 |
if(K.B.l&0x10) K.B.l-=6; \ |
| 167 |
K.B.h=(R->A>>4)-(Rg>>4)-((K.B.l&0x10)>>4); \ |
| 168 |
if(K.B.h&0x10) K.B.h-=6; \ |
| 169 |
R->A=(K.B.l&0x0F)|(K.B.h<<4); \ |
| 170 |
R->P=(R->P&~C_FLAG)|(K.B.h>15? 0:C_FLAG); \ |
| 171 |
} \ |
| 172 |
else \ |
| 173 |
{ \ |
| 174 |
K.W=R->A-Rg-(~R->P&C_FLAG); \ |
| 175 |
R->P&=~(N_FLAG|V_FLAG|Z_FLAG|C_FLAG); \ |
| 176 |
R->P|=((R->A^Rg)&(R->A^K.B.l)&0x80? V_FLAG:0)| \ |
| 177 |
(K.B.h? 0:C_FLAG)|ZNTable[K.B.l]; \ |
| 178 |
R->A=K.B.l; \ |
| 179 |
} |
| 180 |
|
| 181 |
#endif /* NO_DECIMAL */ |
| 182 |
|
| 183 |
#define M_CMP(Rg1,Rg2) \ |
| 184 |
K.W=Rg1-Rg2; \ |
| 185 |
R->P&=~(N_FLAG|Z_FLAG|C_FLAG); \ |
| 186 |
R->P|=ZNTable[K.B.l]|(K.B.h? 0:C_FLAG) |
| 187 |
#define M_BIT(Rg) \ |
| 188 |
R->P&=~(N_FLAG|V_FLAG|Z_FLAG); \ |
| 189 |
R->P|=(Rg&(N_FLAG|V_FLAG))|(Rg&R->A? 0:Z_FLAG) |
| 190 |
|
| 191 |
#define M_AND(Rg) R->A&=Rg;M_FL(R->A) |
| 192 |
#define M_ORA(Rg) R->A|=Rg;M_FL(R->A) |
| 193 |
#define M_EOR(Rg) R->A^=Rg;M_FL(R->A) |
| 194 |
#define M_INC(Rg) Rg++;M_FL(Rg) |
| 195 |
#define M_DEC(Rg) Rg--;M_FL(Rg) |
| 196 |
|
| 197 |
#define M_ASL(Rg) R->P&=~C_FLAG;R->P|=Rg>>7;Rg<<=1;M_FL(Rg) |
| 198 |
#define M_LSR(Rg) R->P&=~C_FLAG;R->P|=Rg&C_FLAG;Rg>>=1;M_FL(Rg) |
| 199 |
#define M_ROL(Rg) K.B.l=(Rg<<1)|(R->P&C_FLAG); \ |
| 200 |
R->P&=~C_FLAG;R->P|=Rg>>7;Rg=K.B.l; \ |
| 201 |
M_FL(Rg) |
| 202 |
#define M_ROR(Rg) K.B.l=(Rg>>1)|(R->P<<7); \ |
| 203 |
R->P&=~C_FLAG;R->P|=Rg&C_FLAG;Rg=K.B.l; \ |
| 204 |
M_FL(Rg) |
| 205 |
|
| 206 |
/** Reset6502() **********************************************/ |
| 207 |
/** This function can be used to reset the registers before **/ |
| 208 |
/** starting execution with Run6502(). It sets registers to **/ |
| 209 |
/** their initial values. **/ |
| 210 |
/*************************************************************/ |
| 211 |
void Reset6502(M6502 *R) |
| 212 |
{ |
| 213 |
R->A=R->X=R->Y=0x00; |
| 214 |
R->P=Z_FLAG|R_FLAG; |
| 215 |
R->S=0xFF; |
| 216 |
R->PC.B.l=Rd6502(0xFFFC); |
| 217 |
R->PC.B.h=Rd6502(0xFFFD); |
| 218 |
R->ICount=R->IPeriod; |
| 219 |
R->IRequest=INT_NONE; |
| 220 |
R->AfterCLI=0; |
| 221 |
} |
| 222 |
|
| 223 |
/** Exec6502() ***********************************************/ |
| 224 |
/** This function will execute a single 6502 opcode. It **/ |
| 225 |
/** will then return next PC, and current register values **/ |
| 226 |
/** in R. **/ |
| 227 |
/*************************************************************/ |
| 228 |
#ifdef EXEC6502 |
| 229 |
int Exec6502(M6502 *R,int RunCycles) |
| 230 |
{ |
| 231 |
register pair J,K; |
| 232 |
register byte I; |
| 233 |
|
| 234 |
/* Execute requested number of cycles */ |
| 235 |
while(RunCycles>0) |
| 236 |
{ |
| 237 |
#ifdef DEBUG |
| 238 |
/* Turn tracing on when reached trap address */ |
| 239 |
if(R->PC.W==R->Trap) R->Trace=1; |
| 240 |
/* Call single-step debugger, exit if requested */ |
| 241 |
if(R->Trace) |
| 242 |
if(!Debug6502(R)) return(RunCycles); |
| 243 |
#endif |
| 244 |
|
| 245 |
I=Op6502(R->PC.W++); |
| 246 |
RunCycles-=Cycles[I]; |
| 247 |
switch(I) |
| 248 |
{ |
| 249 |
#include "Codes.h" |
| 250 |
} |
| 251 |
} |
| 252 |
|
| 253 |
/* Return number of cycles left (<=0) */ |
| 254 |
return(RunCycles); |
| 255 |
} |
| 256 |
#endif /* EXEC6502 */ |
| 257 |
|
| 258 |
/** Int6502() ************************************************/ |
| 259 |
/** This function will generate interrupt of a given type. **/ |
| 260 |
/** INT_NMI will cause a non-maskable interrupt. INT_IRQ **/ |
| 261 |
/** will cause a normal interrupt, unless I_FLAG set in R. **/ |
| 262 |
/*************************************************************/ |
| 263 |
void Int6502(M6502 *R,byte Type) |
| 264 |
{ |
| 265 |
register pair J; |
| 266 |
|
| 267 |
if((Type==INT_NMI)||((Type==INT_IRQ)&&!(R->P&I_FLAG))) |
| 268 |
{ |
| 269 |
R->ICount-=7; |
| 270 |
M_PUSH(R->PC.B.h); |
| 271 |
M_PUSH(R->PC.B.l); |
| 272 |
M_PUSH(R->P&~B_FLAG); |
| 273 |
R->P&=~D_FLAG; |
| 274 |
if(R->IAutoReset&&(Type==R->IRequest)) R->IRequest=INT_NONE; |
| 275 |
if(Type==INT_NMI) J.W=0xFFFA; else { R->P|=I_FLAG;J.W=0xFFFE; } |
| 276 |
R->PC.B.l=Rd6502(J.W++); |
| 277 |
R->PC.B.h=Rd6502(J.W); |
| 278 |
} |
| 279 |
} |
| 280 |
|
| 281 |
/** Run6502() ************************************************/ |
| 282 |
/** This function will run 6502 code until Loop6502() call **/ |
| 283 |
/** returns INT_QUIT. It will return the PC at which **/ |
| 284 |
/** emulation stopped, and current register values in R. **/ |
| 285 |
/*************************************************************/ |
| 286 |
#ifndef EXEC6502 |
| 287 |
word Run6502(M6502 *R) |
| 288 |
{ |
| 289 |
register pair J,K; |
| 290 |
register byte I; |
| 291 |
|
| 292 |
for(;;) |
| 293 |
{ |
| 294 |
#ifdef DEBUG |
| 295 |
/* Turn tracing on when reached trap address */ |
| 296 |
if(R->PC.W==R->Trap) R->Trace=1; |
| 297 |
/* Call single-step debugger, exit if requested */ |
| 298 |
if(R->Trace) |
| 299 |
if(!Debug6502(R)) return(R->PC.W); |
| 300 |
#endif |
| 301 |
|
| 302 |
I=Op6502(R->PC.W++); |
| 303 |
R->ICount-=Cycles[I]; |
| 304 |
switch(I) |
| 305 |
{ |
| 306 |
#include "Codes.h" |
| 307 |
} |
| 308 |
|
| 309 |
/* If cycle counter expired... */ |
| 310 |
if(R->ICount<=0) |
| 311 |
{ |
| 312 |
/* If we have come after CLI, get INT_? from IRequest */ |
| 313 |
/* Otherwise, get it from the loop handler */ |
| 314 |
if(R->AfterCLI) |
| 315 |
{ |
| 316 |
I=R->IRequest; /* Get pending interrupt */ |
| 317 |
R->ICount+=R->IBackup-1; /* Restore the ICount */ |
| 318 |
R->AfterCLI=0; /* Done with AfterCLI state */ |
| 319 |
} |
| 320 |
else |
| 321 |
{ |
| 322 |
I=Loop6502(R); /* Call the periodic handler */ |
| 323 |
R->ICount+=R->IPeriod; /* Reset the cycle counter */ |
| 324 |
if(!I) I=R->IRequest; /* Realize pending interrupt */ |
| 325 |
} |
| 326 |
|
| 327 |
if(I==INT_QUIT) return(R->PC.W); /* Exit if INT_QUIT */ |
| 328 |
if(I) Int6502(R,I); /* Interrupt if needed */ |
| 329 |
} |
| 330 |
} |
| 331 |
|
| 332 |
/* Execution stopped */ |
| 333 |
return(R->PC.W); |
| 334 |
} |
| 335 |
#endif /* !EXEC6502 */ |
Parent Directory
| 
Revision Log