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Fix Decimal Mode (#145) (#148)
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@qbradq @mist64
qbradq authored and mist64 committed Oct 11, 2019
1 parent aab6f77 commit 38ff5fb
Showing 1 changed file with 84 additions and 67 deletions.
151 changes: 84 additions & 67 deletions cpu/instructions.h
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Expand Up @@ -16,44 +16,54 @@
//
static void adc() {
penaltyop = 1;
value = getvalue();
result = (uint16_t)a + value + (uint16_t)(status & FLAG_CARRY);

carrycalc(result);
zerocalc(result);
overflowcalc(result, a, value);
signcalc(result);

#ifndef NES_CPU
if (status & FLAG_DECIMAL) {
clearcarry();

if ((result & 0x0F) > 0x09) {
result += 0x06;
uint16_t tmp, tmp2;
value = getvalue();
tmp = ((uint16_t)a & 0x0F) + (value & 0x0F) + (uint16_t)(status & FLAG_CARRY);
tmp2 = ((uint16_t)a & 0xF0) + (value & 0xF0);
if (tmp > 0x09) {
tmp2 += 0x10;
tmp += 0x06;
}
if ((result & 0xF0) > 0x90) {
result += 0x60;
if (tmp2 > 0x90) {

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@wadaabdulhamid1

wadaabdulhamid1 Oct 15, 2019

var

table
tmp2 += 0x60;
}
if (tmp2 & 0xFF00) {
setcarry();
} else {
clearcarry();
}
result = (tmp & 0x0F) | (tmp2 & 0xF0);

zerocalc(result); /* 65C02 change, Decimal Arithmetic sets NZV */
signcalc(result);

clockticks6502++;
} else {
#endif
value = getvalue();
result = (uint16_t)a + value + (uint16_t)(status & FLAG_CARRY);

carrycalc(result);
zerocalc(result);
overflowcalc(result, a, value);
signcalc(result);
#ifndef NES_CPU
}
#endif

saveaccum(result);
}

static void and() {
penaltyop = 1;
value = getvalue();
result = (uint16_t)a & value;

zerocalc(result);
signcalc(result);

saveaccum(result);
}

Expand All @@ -64,7 +74,7 @@ static void asl() {
carrycalc(result);
zerocalc(result);
signcalc(result);

putvalue(result);
}

Expand Down Expand Up @@ -98,7 +108,7 @@ static void beq() {
static void bit() {
value = getvalue();
result = (uint16_t)a & value;

zerocalc(result);
status = (status & 0x3F) | (uint8_t)(value & 0xC0);
}
Expand Down Expand Up @@ -133,7 +143,7 @@ static void bpl() {
static void brk() {
pc++;


push16(pc); //push next instruction address onto stack
push8(status | FLAG_BREAK); //push CPU status to stack
setinterrupt(); //set interrupt flag
Expand Down Expand Up @@ -179,7 +189,7 @@ static void cmp() {
penaltyop = 1;
value = getvalue();
result = (uint16_t)a - value;

if (a >= (uint8_t)(value & 0x00FF)) setcarry();
else clearcarry();
if (a == (uint8_t)(value & 0x00FF)) setzero();
Expand All @@ -190,7 +200,7 @@ static void cmp() {
static void cpx() {
value = getvalue();
result = (uint16_t)x - value;

if (x >= (uint8_t)(value & 0x00FF)) setcarry();
else clearcarry();
if (x == (uint8_t)(value & 0x00FF)) setzero();
Expand All @@ -201,7 +211,7 @@ static void cpx() {
static void cpy() {
value = getvalue();
result = (uint16_t)y - value;

if (y >= (uint8_t)(value & 0x00FF)) setcarry();
else clearcarry();
if (y == (uint8_t)(value & 0x00FF)) setzero();
Expand All @@ -212,23 +222,23 @@ static void cpy() {
static void dec() {
value = getvalue();
result = value - 1;

zerocalc(result);
signcalc(result);

putvalue(result);
}

static void dex() {
x--;

zerocalc(x);
signcalc(x);
}

static void dey() {
y--;

zerocalc(y);
signcalc(y);
}
Expand All @@ -237,33 +247,33 @@ static void eor() {
penaltyop = 1;
value = getvalue();
result = (uint16_t)a ^ value;

zerocalc(result);
signcalc(result);

saveaccum(result);
}

static void inc() {
value = getvalue();
result = value + 1;

zerocalc(result);
signcalc(result);

putvalue(result);
}

static void inx() {
x++;

zerocalc(x);
signcalc(x);
}

static void iny() {
y++;

zerocalc(y);
signcalc(y);
}
Expand All @@ -281,7 +291,7 @@ static void lda() {
penaltyop = 1;
value = getvalue();
a = (uint8_t)(value & 0x00FF);

zerocalc(a);
signcalc(a);
}
Expand All @@ -290,7 +300,7 @@ static void ldx() {
penaltyop = 1;
value = getvalue();
x = (uint8_t)(value & 0x00FF);

zerocalc(x);
signcalc(x);
}
Expand All @@ -299,20 +309,20 @@ static void ldy() {
penaltyop = 1;
value = getvalue();
y = (uint8_t)(value & 0x00FF);

zerocalc(y);
signcalc(y);
}

static void lsr() {
value = getvalue();
result = value >> 1;

if (value & 1) setcarry();
else clearcarry();
zerocalc(result);
signcalc(result);

putvalue(result);
}

Expand All @@ -333,10 +343,10 @@ static void ora() {
penaltyop = 1;
value = getvalue();
result = (uint16_t)a | value;

zerocalc(result);
signcalc(result);

saveaccum(result);
}

Expand All @@ -350,7 +360,7 @@ static void php() {

static void pla() {
a = pull8();

zerocalc(a);
signcalc(a);
}
Expand All @@ -362,23 +372,23 @@ static void plp() {
static void rol() {
value = getvalue();
result = (value << 1) | (status & FLAG_CARRY);

carrycalc(result);
zerocalc(result);
signcalc(result);

putvalue(result);
}

static void ror() {
value = getvalue();
result = (value >> 1) | ((status & FLAG_CARRY) << 7);

if (value & 1) setcarry();
else clearcarry();
zerocalc(result);
signcalc(result);

putvalue(result);
}

Expand All @@ -395,34 +405,41 @@ static void rts() {

static void sbc() {
penaltyop = 1;
value = getvalue() ^ 0x00FF;
result = (uint16_t)a + value + (uint16_t)(status & FLAG_CARRY);

carrycalc(result);
zerocalc(result);
overflowcalc(result, a, value);
signcalc(result);

#ifndef NES_CPU
if (status & FLAG_DECIMAL) {
clearcarry();

result -= 0x66;
if ((result & 0x0F) > 0x09) {
result += 0x06;
value = getvalue();
result = (uint16_t)a - (value & 0x0f) + (status & FLAG_CARRY) - 1;
if ((result & 0x0f) > (a & 0x0f)) {
result -= 6;
}
if ((result & 0xF0) > 0x90) {
result += 0x60;
result -= (value & 0xf0);
if ((result & 0xfff0) > ((uint16_t)a & 0xf0)) {
result -= 0x60;
}
if (result <= (uint16_t)a) {
setcarry();
} else {
clearcarry();
}

zerocalc(result); /* 65C02 change, Decimal Arithmetic sets NZV */
signcalc(result);

clockticks6502++;
} else {
#endif
value = getvalue() ^ 0x00FF;
result = (uint16_t)a + value + (uint16_t)(status & FLAG_CARRY);

carrycalc(result);
zerocalc(result);
overflowcalc(result, a, value);
signcalc(result);
#ifndef NES_CPU
}
#endif

saveaccum(result);
}

Expand Down Expand Up @@ -452,28 +469,28 @@ static void sty() {

static void tax() {
x = a;

zerocalc(x);
signcalc(x);
}

static void tay() {
y = a;

zerocalc(y);
signcalc(y);
}

static void tsx() {
x = sp;

zerocalc(x);
signcalc(x);
}

static void txa() {
a = x;

zerocalc(a);
signcalc(a);
}
Expand All @@ -484,7 +501,7 @@ static void txs() {

static void tya() {
a = y;

zerocalc(a);
signcalc(a);
}

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