r65emu/r6502.cpp

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

#include "memory.h"
#include "CPU.h"
#include "r6502.h"

void r6502::run(unsigned clocks) {
	while (clocks--) {
		uint8_t op = _mem[PC];
		PC++;
		(this->*_ops[op])();
		if (_halted)
			break;
	}
}

uint8_t 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.flags;
}

char *r6502::status(char *buf, size_t n, bool hdr) {
#if defined(CPU_DEBUG)
	flags();
	snprintf(buf, n,
		"%s%02x %02x %02x %02x %d%d%d%d%d%d%d%d %04x %02x",
		hdr? "aa xx yy sp nv_bdizc _pc_ op\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, (uint8_t)_mem[PC]);
#endif
	return buf;
}

void r6502::checkpoint(Stream &s)
{
#if !defined(NO_CHECKPOINT)
	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.flags);
#endif
}

void r6502::restore(Stream &s)
{
#if !defined(NO_CHECKPOINT)
	uint8_t 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.flags = s.read();
#endif
}

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+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.flags = 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(uint8_t 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(uint8_t 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() {
	--PC;
	_halted = true;
}

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

r6502::r6502(Memory &m): CPU(m) {

	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;
}