tuple<int, vi> strongly_connected_components(const vvi& graph) {
    const int N = graph.size();
    int C = 0, V = 0, top = 0;
    vi comp(N, -1), inx(N, -1), stack(N + 1, -1);

    auto tarjan = [&](auto&& self, int loc) -> int {
        stack[top++] = loc;
        int low = inx[loc] = V++;
        for (int nbr : graph[loc]) {
            if (inx[nbr] == -1) low = min(low, self(self, nbr));
            else if (comp[nbr] == -1) low = min(low, inx[nbr]);
        }
        if (low == inx[loc]) {
            while (stack[top] != loc)
                comp[stack[--top]] = C;
            C++;
        }
        return low;
    };

    for (int i = 0; i < N; i++) {
        if (inx[i] == -1)
            tarjan(tarjan, i);
    }
    return { C, comp };
}
예제 #2
0
static char * INX2() {
    CPU *c = getCPU();
    OP_CODE_INFO *o = getOP_CODE_INFO(0,0,modeImmediate);
    setRegByte(c,IND_X,-103);
    inx(c,o);
    int8_t xVal = getRegByte(c,IND_X);
    mu_assert("INX2 err, IND_X reg != -102", xVal == -102);
    mu_run_test_with_args(testRegStatus,c,"10100000",
            "          NVUBDIZC    NVUBDIZC\nINX2 err, %s != %s");
    freeOP_CODE_INFO(o);
    free(c);
    return 0;
}
예제 #3
0
파일: main.c 프로젝트: ornata/6502
// run appropriate function for opcode in memory
void execute_cpu(machine* mch)
{
	uint8_t *opcode = &mch->memory[mch->pc++];
	uint8_t *memory = mch->memory;

	fprintf(stdout, "opcode: %x\n", opcode[0]);

	switch(*opcode) {
		case 0x02: exit(123);
		case 0x12: exit(123);
		case 0x22: exit(123);
		case 0x32: exit(123);
		case 0x42: exit(123);
		case 0x52: exit(123);
		case 0x62: exit(123);
		case 0x72: exit(123);
		case 0x92: exit(123);
		case 0xB2: exit(123);
		case 0xD2: exit(123);
		case 0xF2: exit(123);
		case 0xEA: return nop(mch, 1);
		case 0x1A: return nop(mch, 2); // illegal instruction (nop with 2 cycles)
		case 0x7A: return nop(mch, 2); // same as above
		case 0x69: return adc_imm(opcode[1], mch);
		case 0x65: return adc_zp(opcode[1], mch);
		case 0x75: return adc_zpx(opcode[1], mch);
		case 0x6D: return adc_abs(opcode[2], opcode[1], mch);
		case 0x7D: return adc_absx(opcode[2], opcode[1], mch);
		case 0x79: return adc_absy(opcode[2], opcode[1], mch);
		case 0x61: return adc_indx(opcode[2], opcode[1], mch);
		case 0x71: return adc_indy(opcode[2], opcode[1], mch);
		case 0x29: return and_imm(opcode[1], mch);
		case 0x25: return and_zp(opcode[1], mch);
		case 0x35: return and_zpx(opcode[1], mch);
		case 0x2D: return and_abs(opcode[2], opcode[1], mch);
		case 0x3D: return and_absx(opcode[2], opcode[1], mch);
		case 0x39: return and_absy(opcode[2], opcode[1], mch);
		case 0x21: return and_indx(opcode[2], opcode[1], mch);
		case 0x31: return and_indy(opcode[2], opcode[1], mch);
		case 0x0A: return asl_acc(mch);
		case 0x06: return asl_zp(opcode[1], mch);
		case 0x16: return asl_zpx(opcode[1], mch);
		case 0x0E: return asl_abs(opcode[2], opcode[1], mch);
		case 0x1E: return asl_absx(opcode[2], opcode[1], mch);
		case 0x90: return branch_clear(opcode[2], opcode[1], mch, 0b00000001);
		case 0xB0: return branch_set(opcode[2], opcode[1], mch, 0b00000001);
		case 0xF0: return branch_set(opcode[2], opcode[1], mch, 0b00000010);
		case 0x24: return bit_zp(opcode[1], mch);
		case 0x2C: return bit_abs(opcode[2], opcode[1], mch);
		case 0x30: return branch_set(opcode[2], opcode[1], mch, 0b10000000);
		case 0xD0: return branch_clear(opcode[2], opcode[1], mch, 0b00000010);
		case 0x10: return branch_clear(opcode[2], opcode[1], mch, 0b10000000);
		case 0x00: return brk(mch);
		case 0x50: return branch_clear(opcode[2], opcode[1], mch, 0b01000000);
		case 0x70: return branch_set(opcode[2], opcode[1], mch, 0b01000000);
		case 0x18: return clc(mch);
		case 0x58: return cli(mch);
		case 0xB8: return clv(mch);
		case 0xC9: return cmp_imm(opcode[1], mch);
		case 0xC5: return cmp_zp(opcode[1], mch);
		case 0xD5: return cmp_zpx(opcode[1], mch);
		case 0xCD: return cmp_abs(opcode[2], opcode[1], mch, 0, 0);
		case 0xDD: return cmp_abs(opcode[2], opcode[1], mch, 1, mch->X);
		case 0xD9: return cmp_abs(opcode[2], opcode[1], mch, 1, mch->Y);
		case 0xC1: return cmp_indy(opcode[2], opcode[1], mch);
		case 0xD1: return cmp_indx(opcode[2], opcode[1], mch);
		case 0xE0: return cpx_imm(opcode[1], mch);
		case 0xE4: return cpx_zp(opcode[1], mch);
		case 0xEC: return cpx_abs(opcode[2], opcode[1], mch);
		case 0xC0: return cpy_imm(opcode[1], mch);
		case 0xC4: return cpy_zp(opcode[1], mch);
		case 0xCC: return cpy_abs(opcode[2], opcode[1], mch);
		case 0xC6: return dec_zp(opcode[1], mch);
		case 0xD6: return dec_zpx(opcode[1], mch);
		case 0xCE: return dec_abs(opcode[2], opcode[1], mch);
		case 0xDE: return dec_absx(opcode[2], opcode[1], mch);
		case 0xCA: return dex(mch);
		case 0x88: return dey(mch);
		case 0x49: return eor_imm(opcode[1], mch);
		case 0x45: return eor_zp(opcode[1], mch);
		case 0x55: return eor_zpx(opcode[1], mch);
		case 0x4D: return eor_abs(opcode[2], opcode[1], mch);
		case 0x5D: return eor_absx(opcode[2], opcode[1], mch);
		case 0x59: return eor_absy(opcode[2], opcode[1], mch);
		case 0x41: return eor_indx(opcode[2], opcode[1], mch);
		case 0x51: return eor_indy(opcode[2], opcode[1], mch);
		case 0xE6: return inc_zp(opcode[1], mch, 0, 0);
		case 0xF6: return inc_zp(opcode[1], mch, 1, mch->X);
		case 0xEE: return inc_abs(opcode[2], opcode[1], mch, 0, 0);
		case 0xFE: return inc_abs(opcode[2], opcode[1], mch, 1, mch->X);
		case 0xE8: return inx(mch);
		case 0xC8: return iny(mch);
		case 0x4C: return jmp_abs(opcode[2], opcode[1], mch);
		case 0x6C: return jmp_ind(opcode[2], opcode[1], mch);
		case 0x20: return jsr(opcode[2], opcode[1], mch);
		case 0xA9: return lda_imm(opcode[1], mch);
		case 0xA5: return lda_zp(opcode[1], mch, 0, 0);
		case 0xB5: return lda_zp(opcode[1], mch, 1, mch->X);
		case 0xAD: return lda_abs(opcode[2], opcode[1], mch, 0, 0);
		case 0xBD: return lda_abs(opcode[2], opcode[1], mch, 1, mch->X);
		case 0xB9: return lda_abs(opcode[2], opcode[1], mch, 1, mch->Y);
		case 0xA1: return lda_indx(opcode[2], opcode[1], mch);
		case 0xB1: return lda_indy(opcode[2], opcode[1], mch);
		case 0xA2: return ldx_imm(opcode[1], mch);
		case 0xA6: return ldx_zp(opcode[1], mch, 0, 0);
		case 0xB6: return ldx_zp(opcode[1], mch, 1, mch->X);
		case 0xAE: return ldx_abs(opcode[2], opcode[1], mch, 0, 0);
		case 0xBE: return ldx_abs(opcode[2], opcode[1], mch, 1, mch->X);
		case 0xA0: return ldy_imm(opcode[1], mch);
		case 0xA4: return ldy_zp(opcode[1], mch, 0, 0);
		case 0xB4: return ldy_zp(opcode[1], mch, 1, mch->X);
		case 0xAC: return ldy_abs(opcode[2], opcode[1], mch, 0, 0);
		case 0xBC: return ldy_abs(opcode[2], opcode[1], mch, 1, mch->X);
		case 0x4A: return lsr_acc(mch);
		case 0x46: return lsr_zp(opcode[1], mch);
		case 0x56: return lsr_zpx(opcode[1], mch);
		case 0x4E: return lsr_abs(opcode[2], opcode[1], mch);
		case 0x5E: return lsr_absx(opcode[2], opcode[1], mch);
		case 0x09: return or_imm(opcode[1], mch);
		case 0x05: return or_zp(opcode[1], mch);
		case 0x15: return or_zpx(opcode[1], mch);
		case 0x0D: return or_abs(opcode[2], opcode[1], mch);
		case 0x1D: return or_absx(opcode[2], opcode[1], mch);
		case 0x19: return or_absy(opcode[2], opcode[1], mch);
		case 0x01: return or_indx(opcode[2], opcode[1], mch);
		case 0x11: return or_indy(opcode[2], opcode[1], mch);
		case 0x48: return pha(mch);
		case 0x08: return php(mch);
		case 0x68: return pla(mch);
		case 0x28: return plp(mch);
		case 0x40: return rti(mch);
		case 0x60: return rts(mch);
		case 0x78: return sei(mch); 
		case 0x38: return sec(mch);
		case 0xAA: return tax(mch);
		case 0xA8: return tay(mch);
		case 0x8A: return txa(mch);
		case 0x98: return tya(mch);

		default:
			fprintf(stdout, "unimplemented opcode!\n");
			fprintf(stdout, "opcode in question: %x\n", opcode[0]);
			exit(1);
			break;
	}
}
예제 #4
0
static void hglin(void) {

	// F53A
	pha();
	c=1;
	sbc(ram[HGR_X]);
	pha();
	a=x;
	sbc(ram[HGR_X+1]);
	ram[HGR_QUADRANT]=a;
	// F544
	if (c==1) goto hglin_1;
	pla();
	a=a^0xff;
	adc(1);
	pha();
	lda_const(0);
	sbc(ram[HGR_QUADRANT]);
	// F550
hglin_1:
	ram[HGR_DX+1]=a;
	ram[HGR_E+1]=a;
	pla();
	ram[HGR_DX]=a;
	ram[HGR_E]=a;
	pla();
	ram[HGR_X]=a;
	ram[HGR_X+1]=x;
	a=y;
	c=0;
	sbc(ram[HGR_Y]);
	if (c==0) goto hglin_2;
	a=a^0xff;
	adc(0xfe);
hglin_2:
	// F568
	ram[HGR_DY]=a;
	ram[HGR_Y]=y;
	ror_mem(HGR_QUADRANT);
	c=1;
	sbc(ram[HGR_DX]);
	x=a;
	lda_const(0xff);
	sbc(ram[HGR_DX+1]);
	ram[HGR_COUNT]=a;
	ldy(HGR_HORIZ);
	goto movex2;	// always?
	// f57c
movex:
	asl();
	move_left_or_right();
	c=1;

	// f581
movex2:
	lda(HGR_E);
	adc(ram[HGR_DY]);
	ram[HGR_E]=a;
	lda(HGR_E+1);
	sbc(0);
movex2_1:
	ram[HGR_E+1]=a;
	lda(y_indirect(GBASL,y));
	a=a^ram[HGR_BITS];
	a=a&ram[HMASK];
	a=a^ram[y_indirect(GBASL,y)];
	ram[y_indirect(GBASL,y)]=a;
	inx();
	if (z!=1) goto movex2_2;
	ram[HGR_COUNT]++;
	if (ram[HGR_COUNT]==0) return;
	// F59e
movex2_2:
	lda(HGR_QUADRANT);
	if (c==1) goto movex;
	move_up_or_down();
	c=0;
	lda(HGR_E);
	adc(ram[HGR_DX]);
	ram[HGR_E]=a;
	lda(HGR_E+1);
	adc(ram[HGR_DX+1]);
	goto movex2_1;
}
예제 #5
0
/** 
 * @brief emulate instruction 
 * @return returns false if something goes wrong (e.g. illegal instruction)
 *
 * Current limitations:
 * 
 * - Illegal instructions are not implemented
 * - Excess cycles due to page boundary crossing are not calculated
 * - Some known architectural bugs are not emulated
 */
bool Cpu::emulate()
{
  /* fetch instruction */
  uint8_t insn = fetch_op();
  bool retval = true;
  /* emulate instruction */
  switch(insn)
  {
  /* BRK */
  case 0x0: brk(); break;
  /* ORA (nn,X) */
  case 0x1: ora(load_byte(addr_indx()),6); break;
  /* ORA nn */
  case 0x5: ora(load_byte(addr_zero()),3); break;
  /* ASL nn */
  case 0x6: asl_mem(addr_zero(),5); break;
  /* PHP */
  case 0x8: php(); break;
  /* ORA #nn */
  case 0x9: ora(fetch_op(),2); break;
  /* ASL A */
  case 0xA: asl_a(); break;
  /* ORA nnnn */
  case 0xD: ora(load_byte(addr_abs()),4); break;
  /* ASL nnnn */
  case 0xE: asl_mem(addr_abs(),6); break; 
  /* BPL nn */
  case 0x10: bpl(); break;
  /* ORA (nn,Y) */
  case 0x11: ora(load_byte(addr_indy()),5); break;
  /* ORA nn,X */
  case 0x15: ora(load_byte(addr_zerox()),4); break;
  /* ASL nn,X */
  case 0x16: asl_mem(addr_zerox(),6); break;
  /* CLC */
  case 0x18: clc(); break;
  /* ORA nnnn,Y */
  case 0x19: ora(load_byte(addr_absy()),4); break;
  /* ORA nnnn,X */
  case 0x1D: ora(load_byte(addr_absx()),4); break;
  /* ASL nnnn,X */
  case 0x1E: asl_mem(addr_absx(),7); break;
  /* JSR */
  case 0x20: jsr(); break;
  /* AND (nn,X) */
  case 0x21: _and(load_byte(addr_indx()),6); break;
  /* BIT nn */
  case 0x24: bit(addr_zero(),3); break;
  /* AND nn */
  case 0x25: _and(load_byte(addr_zero()),3); break;
  /* ROL nn */
  case 0x26: rol_mem(addr_zero(),5); break;
  /* PLP */
  case 0x28: plp(); break;
  /* AND #nn */
  case 0x29: _and(fetch_op(),2); break;
  /* ROL A */
  case 0x2A: rol_a(); break;
  /* BIT nnnn */
  case 0x2C: bit(addr_abs(),4); break;
  /* AND nnnn */
  case 0x2D: _and(load_byte(addr_abs()),4); break;
  /* ROL nnnn */
  case 0x2E: rol_mem(addr_abs(),6); break;
  /* BMI nn */
  case 0x30: bmi(); break;
  /* AND (nn,Y) */
  case 0x31: _and(load_byte(addr_indy()),5); break;               
  /* AND nn,X */
  case 0x35: _and(load_byte(addr_zerox()),4); break;
  /* ROL nn,X */
  case 0x36: rol_mem(addr_zerox(),6); break;
  /* SEC */
  case 0x38: sec(); break;
  /* AND nnnn,Y */
  case 0x39: _and(load_byte(addr_absy()),4); break;
  /* AND nnnn,X */
  case 0x3D: _and(load_byte(addr_absx()),4); break;
  /* ROL nnnn,X */
  case 0x3E: rol_mem(addr_absx(),7); break;
  /* RTI */
  case 0x40: rti(); break;
  /* EOR (nn,X) */
  case 0x41: eor(load_byte(addr_indx()),6); break;
  /* EOR nn */
  case 0x45: eor(load_byte(addr_zero()),3); break;
  /* LSR nn */
  case 0x46: lsr_mem(addr_zero(),5); break;
  /* PHA */
  case 0x48: pha(); break;
  /* EOR #nn */
  case 0x49: eor(fetch_op(),2); break;
  /* BVC */
  case 0x50: bvc(); break;
  /* JMP nnnn */
  case 0x4C: jmp(); break;
  /* EOR nnnn */
  case 0x4D: eor(load_byte(addr_abs()),4); break;
  /* LSR A */
  case 0x4A: lsr_a(); break;
  /* LSR nnnn */
  case 0x4E: lsr_mem(addr_abs(),6); break;
  /* EOR (nn,Y) */
  case 0x51: eor(load_byte(addr_indy()),5); break;
  /* EOR nn,X */
  case 0x55: eor(load_byte(addr_zerox()),4); break;
  /* LSR nn,X */
  case 0x56: lsr_mem(addr_zerox(),6); break;
  /* CLI */
  case 0x58: cli(); break;
  /* EOR nnnn,Y */
  case 0x59: eor(load_byte(addr_absy()),4); break;
  /* EOR nnnn,X */
  case 0x5D: eor(load_byte(addr_absx()),4); break;
  /* LSR nnnn,X */
  case 0x5E: lsr_mem(addr_absx(),7); break;
  /* RTS */
  case 0x60: rts(); break;
  /* ADC (nn,X) */
  case 0x61: adc(load_byte(addr_indx()),6); break;
  /* ADC nn */
  case 0x65: adc(load_byte(addr_zero()),3); break;
  /* ROR nn */
  case 0x66: ror_mem(addr_zero(),5); break;
  /* PLA */
  case 0x68: pla(); break;
  /* ADC #nn */
  case 0x69: adc(fetch_op(),2); break;
  /* ROR A */
  case 0x6A: ror_a(); break;
  /* JMP (nnnn) */
  case 0x6C: jmp_ind(); break;
  /* ADC nnnn */
  case 0x6D: adc(load_byte(addr_abs()),4); break;
  /* ROR nnnn */
  case 0x6E: ror_mem(addr_abs(),6); break;
  /* BVS */
  case 0x70: bvs(); break;
  /* ADC (nn,Y) */
  case 0x71: adc(load_byte(addr_indy()),5); break;
  /* ADC nn,X */
  case 0x75: adc(load_byte(addr_zerox()),4); break;
  /* ROR nn,X */
  case 0x76: ror_mem(addr_zerox(),6); break;
  /* SEI */
  case 0x78: sei(); break;
  /* ADC nnnn,Y */
  case 0x79: adc(load_byte(addr_absy()),4); break;
  /* ADC nnnn,X */
  case 0x7D: adc(load_byte(addr_absx()),4); break;
  /* ROR nnnn,X */
  case 0x7E: ror_mem(addr_absx(),7); break;
  /* STA (nn,X) */
  case 0x81: sta(addr_indx(),6); break;
  /* STY nn */
  case 0x84: sty(addr_zero(),3); break;
  /* STA nn */
  case 0x85: sta(addr_zero(),3); break;
  /* STX nn */
  case 0x86: stx(addr_zero(),3); break;
  /* DEY */
  case 0x88: dey(); break;
  /* TXA */
  case 0x8A: txa(); break;
  /* STY nnnn */
  case 0x8C: sty(addr_abs(),4); break;
  /* STA nnnn */
  case 0x8D: sta(addr_abs(),4); break;
  /* STX nnnn */
  case 0x8E: stx(addr_abs(),4); break;
  /* BCC nn */
  case 0x90: bcc(); break;
  /* STA (nn,Y) */
  case 0x91: sta(addr_indy(),6); break;
  /* STY nn,X */
  case 0x94: sty(addr_zerox(),4); break;
  /* STA nn,X */
  case 0x95: sta(addr_zerox(),4); break;
  /* STX nn,Y */
  case 0x96: stx(addr_zeroy(),4); break;
  /* TYA */
  case 0x98: tya(); break;
  /* STA nnnn,Y */
  case 0x99: sta(addr_absy(),5); break;
  /* TXS */
  case 0x9A: txs(); break;
  /* STA nnnn,X */
  case 0x9D: sta(addr_absx(),5); break;
  /* LDY #nn */
  case 0xA0: ldy(fetch_op(),2); break; 
  /* LDA (nn,X) */
  case 0xA1: lda(load_byte(addr_indx()),6); break;
  /* LDX #nn */
  case 0xA2: ldx(fetch_op(),2); break;
  /* LDY nn */
  case 0xA4: ldy(load_byte(addr_zero()),3); break;
  /* LDA nn */
  case 0xA5: lda(load_byte(addr_zero()),3); break;
  /* LDX nn */
  case 0xA6: ldx(load_byte(addr_zero()),3); break;
  /* TAY */
  case 0xA8: tay(); break;
  /* LDA #nn */
  case 0xA9: lda(fetch_op(),2); break;
  /* TAX */
  case 0xAA: tax(); break;
  /* LDY nnnn */
  case 0xAC: ldy(load_byte(addr_abs()),4); break;
  /* LDA nnnn */
  case 0xAD: lda(load_byte(addr_abs()),4); break;
  /* LDX nnnn */
  case 0xAE: ldx(load_byte(addr_abs()),4); break;
  /* BCS nn */
  case 0xB0: bcs(); break;
  /* LDA (nn,Y) */
  case 0xB1: lda(load_byte(addr_indy()),5); break;
  /* LDY nn,X */
  case 0xB4: ldy(load_byte(addr_zerox()),3); break;
  /* LDA nn,X */
  case 0xB5: lda(load_byte(addr_zerox()),3); break;
  /* LDX nn,Y */
  case 0xB6: ldx(load_byte(addr_zeroy()),3); break;
  /* CLV */
  case 0xB8: clv(); break;
  /* LDA nnnn,Y */
  case 0xB9: lda(load_byte(addr_absy()),4); break;
  /* TSX */
  case 0xBA: tsx(); break;
  /* LDY nnnn,X */
  case 0xBC: ldy(load_byte(addr_absx()),4); break;
  /* LDA nnnn,X */
  case 0xBD: lda(load_byte(addr_absx()),4); break;
  /* LDX nnnn,Y */
  case 0xBE: ldx(load_byte(addr_absy()),4); break;
  /* CPY #nn */
  case 0xC0: cpy(fetch_op(),2); break;
  /* CMP (nn,X) */
  case 0xC1: cmp(load_byte(addr_indx()),6); break;
  /* CPY nn */
  case 0xC4: cpy(load_byte(addr_zero()),3); break;
  /* CMP nn */
  case 0xC5: cmp(load_byte(addr_zero()),3); break;
  /* DEC nn */
  case 0xC6: dec(addr_zero(),5); break;
  /* INY */
  case 0xC8: iny(); break;
  /* CMP #nn */
  case 0xC9: cmp(fetch_op(),2); break;
  /* DEX */
  case 0xCA: dex(); break;
  /* CPY nnnn */
  case 0xCC: cpy(load_byte(addr_abs()),4); break;
  /* CMP nnnn */
  case 0xCD: cmp(load_byte(addr_abs()),4); break;
  /* DEC nnnn */
  case 0xCE: dec(addr_abs(),6); break;
  /* BNE nn */
  case 0xD0: bne(); break;
  /* CMP (nn,Y) */
  case 0xD1: cmp(load_byte(addr_indy()),5); break;
  /* CMP nn,X */
  case 0xD5: cmp(load_byte(addr_zerox()),4); break;
  /* DEC nn,X */
  case 0xD6: dec(addr_zerox(),6); break;
  /* CLD */
  case 0xD8: cld(); break;
  /* CMP nnnn,Y */
  case 0xD9: cmp(load_byte(addr_absy()),4); break;
  /* CMP nnnn,X */
  case 0xDD: cmp(load_byte(addr_absx()),4); break;
  /* DEC nnnn,X */
  case 0xDE: dec(addr_absx(),7); break;
  /* CPX #nn */
  case 0xE0: cpx(fetch_op(),2); break;
  /* SBC (nn,X) */
  case 0xE1: sbc(load_byte(addr_indx()),6); break;
  /* CPX nn */
  case 0xE4: cpx(load_byte(addr_zero()),3); break;
  /* SBC nn */
  case 0xE5: sbc(load_byte(addr_zero()),3); break;
  /* INC nn */
  case 0xE6: inc(addr_zero(),5); break;
  /* INX */
  case 0xE8: inx(); break;
  /* SBC #nn */
  case 0xE9: sbc(fetch_op(),2); break;
  /* NOP */
  case 0xEA: nop(); break;
  /* CPX nnnn */
  case 0xEC: cpx(load_byte(addr_abs()),4); break;
  /* SBC nnnn */
  case 0xED: sbc(load_byte(addr_abs()),4); break;
  /* INC nnnn */
  case 0xEE: inc(addr_abs(),6); break;
  /* BEQ nn */
  case 0xF0: beq(); break;
  /* SBC (nn,Y) */
  case 0xF1: sbc(load_byte(addr_indy()),5); break;
  /* SBC nn,X */
  case 0xF5: sbc(load_byte(addr_zerox()),4); break;
  /* INC nn,X */
  case 0xF6: inc(addr_zerox(),6); break;
  /* SED */
  case 0xF8: sed(); break;
  /* SBC nnnn,Y */
  case 0xF9: sbc(load_byte(addr_absy()),4); break;
  /* SBC nnnn,X */
  case 0xFD: sbc(load_byte(addr_absx()),4); break;
  /* INC nnnn,X */
  case 0xFE: inc(addr_absx(),7); break;
  /* Unknown or illegal instruction */
  default:
    D("Unknown instruction: %X at %04x\n", insn,pc());
    retval = false;
  }
  return retval;
}