/* http://codebase64.org/doku.php?id=base:small_fast_16-bit_prng */
unsigned short random16(void) {
path=0;
path|=PATH_R16;
lda(SEEDL); cycles+=3;
if (a==0) {
cycles+=3;
goto low_zero;
}
cycles+=2;
//lownz:
path|=PATH_LNZ;
asl_mem(SEEDL); cycles+=5;
lda(SEEDH); cycles+=3;
rol(); cycles+=2;
if (c==1) {
cycles+=3;
goto five_cycle_do_eor;
}
cycles+=2;
if (c==0) {
cycles+=3;
goto two_cycle_no_eor;
}
fprintf(stderr,"CAN'T HAPPEN\n");
eleven_cycle_do_eor:
cycles+=6;
five_cycle_do_eor:
cycles+=2;
three_cycle_do_eor:
sta(SEEDH); cycles+=3;
//do_eor:
path|=PATH_DEO;
a=a^0x76; cycles+=2;
sta(SEEDH); cycles+=3;
lda(SEEDL); cycles+=3;
a=a^0x57; cycles+=2;
sta(SEEDL); cycles+=3;
eor_rts:
cycles+=6;
return ((ram[SEEDH]<<8)|ram[SEEDL]);
six_cycles_no_eor:
cycles+=2;
four_cycle_no_eor:
cycles+=2;
two_cycle_no_eor:
cycles+=2;
//no_eor:
cycles+=2;
path|=PATH_NEO;
cycles+=6;
sta(SEEDH); cycles+=3;
cycles+=3;
goto eor_rts;
low_zero:
path|=PATH_LOZ;
lda(SEEDH); cycles+=3;
if (a==0) {
cycles+=3;
goto eleven_cycle_do_eor;
}
cycles+=2;
//ceo:
path|=PATH_CEO;
asl(); cycles+=2;
if (a==0) {
cycles+=3;
goto six_cycles_no_eor;
}
cycles+=2;
//cep:
path|=PATH_CEP;
if (c==0) {
cycles+=3;
goto four_cycle_no_eor;
}
cycles+=2;
if (c==1) {
cycles+=3;
goto three_cycle_do_eor;
}
cycles+=2;
return 0;
}
static void move_up_or_down(void) {
// F4D3
if (n==1) goto move_down;
c=0;
lda(GBASH);
bit(0x1c); // CON.1C
if (z!=1) goto mu_5;
asl_mem(GBASL);
if (c==1) goto mu_3;
bit(0x03); // CON.03
if (z==1) goto mu_1;
adc(0x1f);
c=1;
goto mu_4;
// F4Eb
mu_1:
adc(0x23);
pha();
lda(GBASL);
adc(0xb0);
if (c==1) goto mu_2;
adc(0xf0);
// f4f6
mu_2:
ram[GBASL]=a;
pla();
goto mu_4;
mu_3:
adc(0x1f);
mu_4:
ror_mem(GBASL);
mu_5:
adc(0xfc);
ud_1:
ram[GBASH]=a;
return;
// f505
move_down:
lda(GBASH);
adc(4);
bit(0x1c);
if (z!=1) goto ud_1;
asl_mem(GBASL);
if (c==0) goto md_2;
adc(0xe0);
c=0;
bit(0x4);
if (z==1) goto md_3;
lda(GBASL);
adc(0x50);
a=a^0xf0;
if (a==0) goto md_1;
a=a^0xf0;
md_1:
ram[GBASL]=a;
lda(HGR_PAGE);
goto md_3;
md_2:
adc(0xe0);
md_3:
ror_mem(GBASL);
goto ud_1;
}
/**
* @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;
}