r65emu/r6502.cpp

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

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

#define CPU_STATE_FMT "%02x %02x %02x %02x %d%d%d%d%d%d%d%d	%04x\r",\
		 	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

inline void r6502::step() {
	byte op = _mem[PC];
#ifdef CPU_DEBUG
	if (_debug) {
		flags();
		_status(CPU_STATE_FMT);
	}
#endif
	PC++;
	(this->*_ops[op])();
}

void r6502::run(unsigned clocks) {
#ifdef CPU_DEBUG
	if (_debug) {
		step();
		return;
	}
#endif
	while (clocks--) 
		step();
}

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" CPU_STATE_FMT);
	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;
}