static void hposn(void) {
unsigned char msktbl[]={0x81,0x82,0x84,0x88,0x90,0xA0,0xC0};
// F411
ram[HGR_Y]=a;
ram[HGR_X]=x;
ram[HGR_X+1]=y;
pha();
a=a&0xC0;
ram[GBASL]=a;
lsr();
lsr();
a=a|ram[GBASL];
ram[GBASL]=a;
pla();
// F423
ram[GBASH]=a;
asl();
asl();
asl();
rol_mem(GBASH);
asl();
rol_mem(GBASH);
asl();
ror_mem(GBASL);
lda(GBASH);
a=a&0x1f;
a=a|ram[HGR_PAGE];
ram[GBASH]=a;
// F438
a=x;
cpy(0);
if (z==1) goto hposn_2;
y=35;
adc(4);
hposn_1:
iny();
// f442
hposn_2:
sbc(7);
if (c==1) goto hposn_1;
ram[HGR_HORIZ]=y;
x=a;
a=msktbl[(x-0x100)+7]; // LDA MSKTBL-$100+7,X BIT MASK
// MSKTBL=F5B8
ram[HMASK]=a;
a=y;
lsr();
a=ram[HGR_COLOR];
ram[HGR_BITS]=a;
if (c) color_shift();
}
static void move_left_or_right(void) {
// F465
if (n==0) goto move_right;
a=ram[HMASK];
lsr();
if (c==1) goto lr_2;
a=a^0xc0;
lr_1:
ram[HMASK]=a;
return;
lr_2:
dey();
if (n==0) goto lr_3;
y=39;
lr_3:
a=0xc0;
lr_4:
ram[HMASK]=a;
ram[HGR_HORIZ]=y;
a=ram[HGR_BITS];
color_shift();
return;
move_right:
a=ram[HMASK];
asl();
a=a^0x80;
if (a&0x80) goto lr_1;
a=0x81;
iny();
cpy(40);
if (c==0) goto lr_4;
y=0;
goto lr_4;
}
// 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;
}
}
/**
* @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;
}