r65emu/r6502.cpp

#include <stdio.h>
#include <Stream.h>

#include "memory.h"
#include "cpu.h"
#include "r6502.h"

Memory::address r6502::run (unsigned clocks) {
  while (clocks--) 
  {
    byte op = (*_memory)[PC];
#ifdef CPU_DEBUG
    if (_debug)
      _status ("%04x: %02x [%02x %02x %02x, %02x]\r", PC, op, A, X, Y, flags());
#endif
    PC++;
    (this->*_ops[op])();
  }
  return PC;
}

byte r6502::flags() {
  P.bits.N = ((N & 0x80) != 0);
  P.bits.V = V;
  P.bits.Z = !Z;
  P.bits.C = C;
  P.bits._ = 1;
  return P.value;
}

char *r6502::status () {
  static char buf[128];
  flags();
  sprintf (buf, "aa xx yy sp nv_bdizc  _pc_\r\n"
     "%02x %02x %02x %02x %d%d%d%d%d%d%d%d  %04x\r\n", 
     A, X, Y, S, P.bits.N, P.bits.V, P.bits._, P.bits.B, 
     P.bits.D, P.bits.I, P.bits.Z, P.bits.C, PC);
  return buf;
}

void r6502::checkpoint(Stream &s)
{
  s.write(PC / 0xff);
  s.write(PC % 0xff);
  s.write(S);  
  s.write(A);  
  s.write(X);  
  s.write(Y);  
  s.write(N);  
  s.write(V);  
  s.write(B);  
  s.write(D);  
  s.write(I);  
  s.write(Z);  
  s.write(C);  
  s.write(P.value);  
}

void r6502::restore(Stream &s)
{
  byte hi = s.read(), lo = s.read();
  PC = hi * 0xff + lo;
  S = s.read();
  A = s.read();
  X = s.read();
  Y = s.read();
  N = s.read();
  V = s.read();
  B = s.read();
  D = s.read();
  I = s.read();
  Z = s.read();
  C = s.read();
  P.value = s.read();
}

void r6502::raise (int level) {
  if (level < 0)
    nmi ();
  else if (!P.bits.I)
    irq ();
  else
    _irq = true;
}

void r6502::irq () {
  pusha (PC);
  P.bits.B = 0;
  pushb (flags ());
  P.bits.B = 1;
  P.bits.I = 1;
  PC = vector (ibvec);
  _irq = false;
}

void r6502::brk () {
  if (!P.bits.I) {
    pusha (PC);
    P.bits.B = 1;
    php ();
    P.bits.I = 1;
    PC = vector (ibvec);
  }
  P.bits.B = 1;
  P.bits._ = 1;
}

void r6502::rti () {
  plp ();
  PC = popa ();
}

void r6502::cli () {
  P.bits.I = 0;
  if (_irq)
    irq();
}

void r6502::nmi () {
  pusha (PC);
  php ();
  P.bits.I = 1;
  PC = vector (nmivec);
}

// php and plp are complicated by the representation
// of the processor state for efficient normal operation
void r6502::php () {
  P.bits.B = 1;
  pushb (flags ());
}

void r6502::plp () {
  P.value = popb ();
  N = P.bits.N? 0x80: 0;
  V = P.bits.V;
  Z = !P.bits.Z;
  C = P.bits.C;
}

void r6502::rts () {
  PC = popa ()+1;
}

void r6502::jsr () {
  pusha (PC+1);
  PC = vector (PC);
}

void r6502::_adc (byte d) {
  if (P.bits.D) {
    int r = _fromBCD[A] + _fromBCD[d] + C;
    C = (r > 99);
    if (C) r -= 100;
    A = _toBCD[r];
  } else {
    unsigned short u = (unsigned short)A + (unsigned short)d + (unsigned short)C;
    short s = (char)A + (char)d + (char)C;
    C = (u < 0 || u > 255);
    V = (s > 127 || s < -128);
    A = (u & 0xff);
  }
  N = (A & 0x80);
  Z = A;
}

void r6502::sbcd (byte d) {
  int r = _fromBCD[A] - _fromBCD[d] - !C;
  C = (r >= 0);
  if (r < 0) r += 100;
  A = _toBCD[r & 0xff];
  N = (A & 0x80);
  Z = A;
  // V not tested for: http://www.6502.org/tutorials/decimal_mode.html
}

void r6502::ill () {
  _status ("Illegal instruction at %04x!\r\n%s", (PC-1), status());
  longjmp (*_err, 1);
}

void r6502::reset ()
{
  _debug = false;
  P.value = 0;
  P.bits._ = 1;
  P.bits.B = 1;
  _irq = false;
  S = 0xff;
  PC = vector(resvec);
}

r6502::r6502 (Memory *m, jmp_buf *e, CPU::statfn s): CPU (m,e,s) {

  for (int i=0; i < 256; i++) {
    _fromBCD[i] = ((i >> 4) & 0x0f)*10 + (i & 0x0f);
    _toBCD[i] = (((i % 100) / 10) << 4) | (i % 10);
  }
    
  OP *p = _ops;
  *p++=&r6502::brk; *p++=&r6502::ora_ix; *p++=&r6502::ill; *p++=&r6502::ill; 
  *p++=&r6502::nop2; *p++=&r6502::ora_z; *p++=&r6502::asl_z; *p++=&r6502::ill;
  *p++=&r6502::php; *p++=&r6502::ora_; *p++=&r6502::asl; *p++=&r6502::ill; 
  *p++=&r6502::nop3; *p++=&r6502::ora_a; *p++=&r6502::asl_a; *p++=&r6502::ill;
  *p++=&r6502::bpl; *p++=&r6502::ora_iy; *p++=&r6502::ill; *p++=&r6502::ill; 
  *p++=&r6502::nop2; *p++=&r6502::ora_zx; *p++=&r6502::asl_zx; *p++=&r6502::ill;
  *p++=&r6502::clc; *p++=&r6502::ora_ay; *p++=&r6502::nop; *p++=&r6502::ill; 
  *p++=&r6502::nop2; *p++=&r6502::ora_ax; *p++=&r6502::asl_ax; *p++=&r6502::ill;
  *p++=&r6502::jsr; *p++=&r6502::and_ix; *p++=&r6502::ill; *p++=&r6502::ill; 
  *p++=&r6502::bit_z; *p++=&r6502::and_z; *p++=&r6502::rol_z; *p++=&r6502::ill;
  *p++=&r6502::plp; *p++=&r6502::and_; *p++=&r6502::rol; *p++=&r6502::ill; 
  *p++=&r6502::bit_a; *p++=&r6502::and_a; *p++=&r6502::rol_a; *p++=&r6502::ill;
  *p++=&r6502::bmi; *p++=&r6502::and_iy; *p++=&r6502::ill; *p++=&r6502::ill; 
  *p++=&r6502::nop2; *p++=&r6502::and_zx; *p++=&r6502::rol_zx; *p++=&r6502::ill;
  *p++=&r6502::sec; *p++=&r6502::and_ay; *p++=&r6502::nop; *p++=&r6502::ill; 
  *p++=&r6502::nop3; *p++=&r6502::and_ax; *p++=&r6502::rol_ax; *p++=&r6502::ill;
  *p++=&r6502::rti; *p++=&r6502::eor_ix; *p++=&r6502::ill; *p++=&r6502::ill; 
  *p++=&r6502::nop2; *p++=&r6502::eor_z; *p++=&r6502::lsr_z; *p++=&r6502::ill;
  *p++=&r6502::pha; *p++=&r6502::eor_; *p++=&r6502::lsr_; *p++=&r6502::ill; 
  *p++=&r6502::jmp; *p++=&r6502::eor_a; *p++=&r6502::lsr_a; *p++=&r6502::ill;
  *p++=&r6502::bvc; *p++=&r6502::eor_iy; *p++=&r6502::ill; *p++=&r6502::ill; 
  *p++=&r6502::nop2; *p++=&r6502::eor_zx; *p++=&r6502::lsr_zx; *p++=&r6502::ill;
  *p++=&r6502::cli; *p++=&r6502::eor_ay; *p++=&r6502::nop; *p++=&r6502::ill; 
  *p++=&r6502::nop3; *p++=&r6502::eor_ax; *p++=&r6502::lsr_ax; *p++=&r6502::ill;
  *p++=&r6502::rts; *p++=&r6502::adc_ix; *p++=&r6502::ill; *p++=&r6502::ill; 
  *p++=&r6502::nop2; *p++=&r6502::adc_z; *p++=&r6502::ror_z; *p++=&r6502::ill;
  *p++=&r6502::pla; *p++=&r6502::adc_; *p++=&r6502::ror_; *p++=&r6502::ill; 
  *p++=&r6502::jmp_i; *p++=&r6502::adc_a; *p++=&r6502::ror_a; *p++=&r6502::ill;
  *p++=&r6502::bvs; *p++=&r6502::adc_iy; *p++=&r6502::ill; *p++=&r6502::ill; 
  *p++=&r6502::nop2; *p++=&r6502::adc_zx; *p++=&r6502::ror_zx; *p++=&r6502::ill;
  *p++=&r6502::sei; *p++=&r6502::adc_ay; *p++=&r6502::nop; *p++=&r6502::ill; 
  *p++=&r6502::nop3; *p++=&r6502::adc_ax; *p++=&r6502::ror_ax; *p++=&r6502::ill;
  *p++=&r6502::nop2; *p++=&r6502::sta_ix; *p++=&r6502::nop2; *p++=&r6502::ill; 
  *p++=&r6502::sty_z; *p++=&r6502::sta_z; *p++=&r6502::stx_z; *p++=&r6502::ill;
  *p++=&r6502::dey; *p++=&r6502::nop2; *p++=&r6502::txa; *p++=&r6502::ill; 
  *p++=&r6502::sty_a; *p++=&r6502::sta_a; *p++=&r6502::stx_a; *p++=&r6502::ill;
  *p++=&r6502::bcc; *p++=&r6502::sta_iy; *p++=&r6502::ill; *p++=&r6502::ill; 
  *p++=&r6502::sty_zx; *p++=&r6502::sta_zx; *p++=&r6502::stx_zy; *p++=&r6502::ill;
  *p++=&r6502::tya; *p++=&r6502::sta_ay; *p++=&r6502::txs; *p++=&r6502::ill; 
  *p++=&r6502::ill; *p++=&r6502::sta_ax; *p++=&r6502::ill; *p++=&r6502::ill;
  *p++=&r6502::ldy_; *p++=&r6502::lda_ix; *p++=&r6502::ldx_; *p++=&r6502::lax_ix; 
  *p++=&r6502::ldy_z; *p++=&r6502::lda_z; *p++=&r6502::ldx_z; *p++=&r6502::lax_z;
  *p++=&r6502::tay; *p++=&r6502::lda_; *p++=&r6502::tax; *p++=&r6502::ill; 
  *p++=&r6502::ldy_a; *p++=&r6502::lda_a; *p++=&r6502::ldx_a; *p++=&r6502::lax_a;
  *p++=&r6502::bcs; *p++=&r6502::lda_iy; *p++=&r6502::ill; *p++=&r6502::lax_iy; 
  *p++=&r6502::ldy_zx; *p++=&r6502::lda_zx; *p++=&r6502::ldx_zy; *p++=&r6502::lax_zy;
  *p++=&r6502::clv; *p++=&r6502::lda_ay; *p++=&r6502::tsx; *p++=&r6502::ill; 
  *p++=&r6502::ldy_ax; *p++=&r6502::lda_ax; *p++=&r6502::ldx_ay; *p++=&r6502::lax_ay;
  *p++=&r6502::cpy_; *p++=&r6502::cmp_ix; *p++=&r6502::nop2; *p++=&r6502::ill; 
  *p++=&r6502::cpy_z; *p++=&r6502::cmp_z; *p++=&r6502::dec_z; *p++=&r6502::ill;
  *p++=&r6502::iny; *p++=&r6502::cmp_; *p++=&r6502::dex; *p++=&r6502::ill; 
  *p++=&r6502::cpy_a; *p++=&r6502::cmp_a; *p++=&r6502::dec_a; *p++=&r6502::ill;
  *p++=&r6502::bne; *p++=&r6502::cmp_iy; *p++=&r6502::ill; *p++=&r6502::ill; 
  *p++=&r6502::nop2; *p++=&r6502::cmp_zx; *p++=&r6502::dec_zx; *p++=&r6502::ill;
  *p++=&r6502::cld; *p++=&r6502::cmp_ay; *p++=&r6502::nop; *p++=&r6502::ill; 
  *p++=&r6502::nop3; *p++=&r6502::cmp_ax; *p++=&r6502::dec_ax; *p++=&r6502::ill;
  *p++=&r6502::cpx_; *p++=&r6502::sbc_ix; *p++=&r6502::nop2; *p++=&r6502::ill; 
  *p++=&r6502::cpx_z; *p++=&r6502::sbc_z; *p++=&r6502::inc_z; *p++=&r6502::ill;
  *p++=&r6502::inx; *p++=&r6502::sbc_; *p++=&r6502::nop; *p++=&r6502::ill; 
  *p++=&r6502::cpx_a; *p++=&r6502::sbc_a; *p++=&r6502::inc_a; *p++=&r6502::ill;
  *p++=&r6502::beq; *p++=&r6502::sbc_iy; *p++=&r6502::ill; *p++=&r6502::ill; 
  *p++=&r6502::nop2; *p++=&r6502::sbc_zx; *p++=&r6502::inc_zx; *p++=&r6502::ill;
  *p++=&r6502::sed; *p++=&r6502::sbc_ay; *p++=&r6502::nop; *p++=&r6502::ill; 
  *p++=&r6502::nop3; *p++=&r6502::sbc_ax; *p++=&r6502::inc_ax; *p++=&r6502::ill;
}