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Function for updating N and Z flags
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@Shachar
Shachar committed Sep 12, 2023
1 parent 4ef15f0 commit 65c3853
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Showing 2 changed files with 37 additions and 62 deletions.
97 changes: 35 additions & 62 deletions c6502.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -414,16 +414,14 @@ void c6502::op_adc(Addr addr) {

regA = val;

ccSet( CC::Zero, regA==0 );
ccSet( CC::Carry, val & 0x100 );
ccSet( CC::Negative, val & 0x80 );
updateNZ( val );
}

void c6502::op_and(Addr addr) {
regA &= read(addr);

ccSet( CC::Negative, regA & 0x80 );
ccSet( CC::Zero, regA==0 );
updateNZ( regA );
}

void c6502::op_asl(Addr addr) {
Expand All @@ -433,9 +431,7 @@ void c6502::op_asl(Addr addr) {

ccSet( CC::Carry, val&0x100 );

val &= 0xff;
ccSet( CC::Negative, val&0x80 );
ccSet( CC::Zero, val==0 );
updateNZ( val );

write(addr, val);
}
Expand All @@ -449,9 +445,7 @@ void c6502::op_aslA() {

ccSet( CC::Carry, val&0x100 );

val &= 0xff;
ccSet( CC::Negative, val&0x80 );
ccSet( CC::Zero, val==0 );
updateNZ( val );

regA = val;
}
Expand Down Expand Up @@ -531,26 +525,23 @@ void c6502::op_cmp(Addr addr) {
uint16_t calc = 0x100 | regA;
calc -= read(addr);

ccSet( CC::Negative, calc & 0x80 );
ccSet( CC::Zero, (calc & 0xff) == 0 );
ccSet( CC::Carry, calc & 0x100 );
updateNZ( calc );
}

void c6502::op_cpx(Addr addr) {
uint16_t calc = 0x100 | regX;
calc -= read(addr);

ccSet( CC::Negative, calc & 0x80 );
ccSet( CC::Zero, (calc & 0xff) == 0 );
updateNZ( calc );
ccSet( CC::Carry, calc & 0x100 );
}

void c6502::op_cpy(Addr addr) {
uint16_t calc = 0x100 | regY;
calc -= read(addr);

ccSet( CC::Negative, calc & 0x80 );
ccSet( CC::Zero, (calc & 0xff) == 0 );
updateNZ( calc );
ccSet( CC::Carry, calc & 0x100 );
}

Expand All @@ -561,36 +552,31 @@ void c6502::op_dec(Addr addr) {
res--;
write(addr, res);

ccSet( CC::Negative, res&0x80 );
ccSet( CC::Zero, res==0 );
updateNZ( res );
}

void c6502::op_decA(Addr addr) {
regX--;

ccSet( CC::Negative, regX & 0x80 );
ccSet( CC::Zero, regX==0 );
updateNZ( regX );
}

void c6502::op_dex(Addr addr) {
regX--;

ccSet( CC::Negative, regX & 0x80 );
ccSet( CC::Zero, regX==0 );
updateNZ( regX );
}

void c6502::op_dey(Addr addr) {
regY--;

ccSet( CC::Negative, regY & 0x80 );
ccSet( CC::Zero, regY==0 );
updateNZ( regY );
}

void c6502::op_eor(Addr addr) {
regA ^= read(addr);

ccSet( CC::Negative, regA & 0x80 );
ccSet( CC::Zero, regA==0 );
updateNZ( regA );
}

void c6502::op_inc(Addr addr) {
Expand All @@ -599,29 +585,25 @@ void c6502::op_inc(Addr addr) {
write(addr, val);
write(addr, ++val);

ccSet( CC::Negative, val & 0x80 );
ccSet( CC::Zero, val==0 );
updateNZ( val );
}

void c6502::op_incA(Addr addr) {
regA++;

ccSet( CC::Negative, regA & 0x80 );
ccSet( CC::Zero, regA==0 );
updateNZ( regA );
}

void c6502::op_inx(Addr addr) {
regX++;

ccSet( CC::Negative, regX & 0x80 );
ccSet( CC::Zero, regX==0 );
updateNZ( regX );
}

void c6502::op_iny(Addr addr) {
regY++;

ccSet( CC::Negative, regY & 0x80 );
ccSet( CC::Zero, regY==0 );
updateNZ( regY );
}

void c6502::op_jmp(Addr addr) {
Expand All @@ -644,22 +626,19 @@ void c6502::op_jsr(Addr addr) {
void c6502::op_lda(Addr addr) {
regA = read( addr );

ccSet( CC::Zero, regA==0 );
ccSet( CC::Negative, regA & 0x80 );
updateNZ( regA );
}

void c6502::op_ldx(Addr addr) {
regX = read( addr );

ccSet( CC::Zero, regX==0 );
ccSet( CC::Negative, regX & 0x80 );
updateNZ( regX );
}

void c6502::op_ldy(Addr addr) {
regY = read( addr );

ccSet( CC::Zero, regY==0 );
ccSet( CC::Negative, regY & 0x80 );
updateNZ( regY );
}

void c6502::op_lsr(Addr addr) {
Expand All @@ -669,8 +648,7 @@ void c6502::op_lsr(Addr addr) {
ccSet( CC::Carry, val&0x01 );
val >>= 1;

ccSet( CC::Negative, val&0x80 );
ccSet( CC::Zero, val==0 );
updateNZ( val );

write(addr, val);
}
Expand All @@ -682,8 +660,7 @@ void c6502::op_lsrA() {

regA >>= 1;

ccSet( CC::Negative, regA&0x80 );
ccSet( CC::Zero, regA==0 );
updateNZ( regA );
}

void c6502::op_nop(Addr addr) {
Expand All @@ -692,8 +669,7 @@ void c6502::op_nop(Addr addr) {
void c6502::op_ora(Addr addr) {
regA |= read(addr);

ccSet( CC::Negative, regA & 0x80 );
ccSet( CC::Zero, regA==0 );
updateNZ( regA );
}


Expand All @@ -715,8 +691,7 @@ void c6502::op_pla(Addr addr) {
regSp++;
regA = read( compose( 0x01, regSp ) );

ccSet( CC::Negative, regA & 0x80 );
ccSet( CC::Zero, regA==0 );
updateNZ( regA );
}

void c6502::op_plp(Addr addr) {
Expand All @@ -733,8 +708,7 @@ void c6502::op_rol(Addr addr) {
value <<= 1;
value |= ccGet( CC::Carry );
ccSet( CC::Carry, value & 0x100 );
ccSet( CC::Negative, value & 0x80 );
ccSet( CC::Zero, (value&0xff)==0 );
updateNZ( value );

write( addr, value );
}
Expand All @@ -748,8 +722,7 @@ void c6502::op_rolA() {
regA |= 0x01;

ccSet( CC::Carry, newC );
ccSet( CC::Negative, regA & 0x80 );
ccSet( CC::Zero, regA==0 );
updateNZ( regA );
}

void c6502::op_rti(Addr addr) {
Expand Down Expand Up @@ -786,9 +759,8 @@ void c6502::op_sbc(Addr addr) {

ccSet( CC::oVerflow, !sameSign && stillSameSign );

ccSet( CC::Zero, regA==0 );
updateNZ( regA );
ccSet( CC::Carry, (res & 0x100)==0 );
ccSet( CC::Negative, res & 0x80 );
}

void c6502::op_sec(Addr addr) {
Expand Down Expand Up @@ -820,33 +792,34 @@ void c6502::op_tax() {

regX = regA;

ccSet( CC::Zero, regA==0 );
ccSet( CC::Negative, regA & 0x80 );
updateNZ( regA );
}

void c6502::op_tay() {
read( pc() );

regY = regA;

ccSet( CC::Zero, regA==0 );
ccSet( CC::Negative, regA & 0x80 );
updateNZ( regA );
}

void c6502::op_txa(Addr addr) {
regA = regX;

ccSet( CC::Zero, regA==0 );
ccSet( CC::Negative, regA & 0x80 );
updateNZ( regA );
}

void c6502::op_tya(Addr addr) {
regA = regY;

ccSet( CC::Zero, regA==0 );
ccSet( CC::Negative, regA & 0x80 );
updateNZ( regA );
}

void c6502::op_txs(Addr addr) {
regSp = regX;
}

void c6502::updateNZ(uint8_t val) {
ccSet( CC::Negative, val & 0x80 );
ccSet( CC::Zero, val == 0 );
}
2 changes: 2 additions & 0 deletions c6502.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -131,4 +131,6 @@ class c6502 {
void op_txa(Addr addr);
void op_txs(Addr addr);
void op_tya(Addr addr);

void updateNZ(uint8_t val);
};

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