Updated CPU Module
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0xmac
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156
src/cpu.c
156
src/cpu.c
@ -12,14 +12,6 @@ extern uint8_t read6502(uint16_t address);
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extern void write6502(uint16_t address, uint8_t value);
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extern void write6502(uint16_t address, uint8_t value);
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//6502 defines
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//6502 defines
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#define UNDOCUMENTED //when this is defined, undocumented opcodes are handled.
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//otherwise, they're simply treated as NOPs.
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//#define NES_CPU //when this is defined, the binary-coded decimal (BCD)
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//status flag is not honored by ADC and SBC. the 2A03
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//CPU in the Nintendo Entertainment System does not
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//support BCD operation.
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#define FLAG_CARRY 0x01
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#define FLAG_CARRY 0x01
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#define FLAG_ZERO 0x02
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#define FLAG_ZERO 0x02
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#define FLAG_INTERRUPT 0x04
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#define FLAG_INTERRUPT 0x04
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@ -77,10 +69,17 @@ uint8_t sp, a, x, y, status = FLAG_CONSTANT;
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//helper variables
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//helper variables
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uint64_t instructions = 0; //keep track of total instructions executed
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uint32_t clockticks6502 = 0;
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uint32_t clockticks6502 = 0, clockgoal6502 = 0;
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uint32_t clockgoal6502 = 0;
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uint16_t oldpc, ea, reladdr, value, result;
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uint8_t opcode, oldstatus;
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uint16_t oldpc;
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uint16_t ea;
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uint16_t reladdr;
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uint16_t value;
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uint16_t result;
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uint8_t opcode;
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uint8_t oldstatus;
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//a few general functions used by various other functions
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//a few general functions used by various other functions
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void push16(uint16_t pushval) {
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void push16(uint16_t pushval) {
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@ -157,7 +156,7 @@ static void absx() { //absolute,X
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startpage = ea & 0xFF00;
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startpage = ea & 0xFF00;
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ea += (uint16_t)x;
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ea += (uint16_t)x;
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if (startpage != (ea & 0xFF00)) { //one cycle penlty for page-crossing on some opcodes
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if (startpage != (ea & 0xFF00)) { //one cycle penalty for page-crossing on some opcodes
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penaltyaddr = 1;
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penaltyaddr = 1;
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}
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}
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@ -226,22 +225,6 @@ static void adc() {
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overflowcalc(result, a, value);
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overflowcalc(result, a, value);
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signcalc(result);
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signcalc(result);
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#ifndef NES_CPU
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if (status & FLAG_DECIMAL) {
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clearcarry();
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if ((a & 0x0F) > 0x09) {
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a += 0x06;
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}
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if ((a & 0xF0) > 0x90) {
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a += 0x60;
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setcarry();
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}
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clockticks6502++;
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}
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#endif
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saveaccum(result);
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saveaccum(result);
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}
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}
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@ -572,6 +555,7 @@ static void ror() {
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if (value & 1) setcarry();
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if (value & 1) setcarry();
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else clearcarry();
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else clearcarry();
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zerocalc(result);
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zerocalc(result);
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signcalc(result);
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signcalc(result);
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@ -599,23 +583,6 @@ static void sbc() {
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overflowcalc(result, a, value);
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overflowcalc(result, a, value);
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signcalc(result);
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signcalc(result);
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#ifndef NES_CPU
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if (status & FLAG_DECIMAL) {
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clearcarry();
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a -= 0x66;
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if ((a & 0x0F) > 0x09) {
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a += 0x06;
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}
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if ((a & 0xF0) > 0x90) {
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a += 0x60;
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setcarry();
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}
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clockticks6502++;
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}
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#endif
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saveaccum(result);
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saveaccum(result);
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}
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}
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@ -682,67 +649,6 @@ static void tya() {
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signcalc(a);
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signcalc(a);
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}
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}
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//undocumented instructions
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#ifdef UNDOCUMENTED
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static void lax() {
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lda();
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ldx();
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}
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static void sax() {
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sta();
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stx();
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putvalue(a & x);
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if (penaltyop && penaltyaddr) clockticks6502--;
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}
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static void dcp() {
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dec();
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cmp();
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if (penaltyop && penaltyaddr) clockticks6502--;
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}
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static void isb() {
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inc();
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sbc();
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if (penaltyop && penaltyaddr) clockticks6502--;
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}
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static void slo() {
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asl();
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ora();
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if (penaltyop && penaltyaddr) clockticks6502--;
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}
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static void rla() {
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rol();
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and();
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if (penaltyop && penaltyaddr) clockticks6502--;
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}
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static void sre() {
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lsr();
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eor();
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if (penaltyop && penaltyaddr) clockticks6502--;
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}
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static void rra() {
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ror();
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adc();
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if (penaltyop && penaltyaddr) clockticks6502--;
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}
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#else
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#define lax nop
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#define sax nop
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#define dcp nop
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#define isb nop
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#define slo nop
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#define rla nop
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#define sre nop
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#define rra nop
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#endif
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static void (*addrtable[256])() = {
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static void (*addrtable[256])() = {
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/* | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | */
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/* | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | */
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/* 0 */ imp, indx, imp, indx, zp, zp, zp, zp, imp, imm, acc, imm, abso, abso, abso, abso, /* 0 */
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/* 0 */ imp, indx, imp, indx, zp, zp, zp, zp, imp, imm, acc, imm, abso, abso, abso, abso, /* 0 */
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@ -765,22 +671,22 @@ static void (*addrtable[256])() = {
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static void (*optable[256])() = {
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static void (*optable[256])() = {
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/* | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | */
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/* | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | */
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/* 0 */ brk, ora, nop, slo, nop, ora, asl, slo, php, ora, asl, nop, nop, ora, asl, slo, /* 0 */
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/* 0 */ brk, ora, nop, nop, nop, ora, asl, nop, php, ora, asl, nop, nop, ora, asl, nop, /* 0 */
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/* 1 */ bpl, ora, nop, slo, nop, ora, asl, slo, clc, ora, nop, slo, nop, ora, asl, slo, /* 1 */
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/* 1 */ bpl, ora, nop, nop, nop, ora, asl, nop, clc, ora, nop, nop, nop, ora, asl, nop, /* 1 */
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/* 2 */ jsr, and, nop, rla, bit, and, rol, rla, plp, and, rol, nop, bit, and, rol, rla, /* 2 */
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/* 2 */ jsr, and, nop, nop, bit, and, rol, nop, plp, and, rol, nop, bit, and, rol, nop, /* 2 */
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/* 3 */ bmi, and, nop, rla, nop, and, rol, rla, sec, and, nop, rla, nop, and, rol, rla, /* 3 */
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/* 3 */ bmi, and, nop, nop, nop, and, rol, nop, sec, and, nop, nop, nop, and, rol, nop, /* 3 */
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/* 4 */ rti, eor, nop, sre, nop, eor, lsr, sre, pha, eor, lsr, nop, jmp, eor, lsr, sre, /* 4 */
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/* 4 */ rti, eor, nop, nop, nop, eor, lsr, nop, pha, eor, lsr, nop, jmp, eor, lsr, nop, /* 4 */
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/* 5 */ bvc, eor, nop, sre, nop, eor, lsr, sre, cli, eor, nop, sre, nop, eor, lsr, sre, /* 5 */
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/* 5 */ bvc, eor, nop, nop, nop, eor, lsr, nop, cli, eor, nop, nop, nop, eor, lsr, nop, /* 5 */
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/* 6 */ rts, adc, nop, rra, nop, adc, ror, rra, pla, adc, ror, nop, jmp, adc, ror, rra, /* 6 */
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/* 6 */ rts, adc, nop, nop, nop, adc, ror, nop, pla, adc, ror, nop, jmp, adc, ror, nop, /* 6 */
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/* 7 */ bvs, adc, nop, rra, nop, adc, ror, rra, sei, adc, nop, rra, nop, adc, ror, rra, /* 7 */
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/* 7 */ bvs, adc, nop, nop, nop, adc, ror, nop, sei, adc, nop, nop, nop, adc, ror, nop, /* 7 */
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/* 8 */ nop, sta, nop, sax, sty, sta, stx, sax, dey, nop, txa, nop, sty, sta, stx, sax, /* 8 */
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/* 8 */ nop, sta, nop, nop, sty, sta, stx, nop, dey, nop, txa, nop, sty, sta, stx, nop, /* 8 */
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/* 9 */ bcc, sta, nop, nop, sty, sta, stx, sax, tya, sta, txs, nop, nop, sta, nop, nop, /* 9 */
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/* 9 */ bcc, sta, nop, nop, sty, sta, stx, nop, tya, sta, txs, nop, nop, sta, nop, nop, /* 9 */
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/* A */ ldy, lda, ldx, lax, ldy, lda, ldx, lax, tay, lda, tax, nop, ldy, lda, ldx, lax, /* A */
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/* A */ ldy, lda, ldx, nop, ldy, lda, ldx, nop, tay, lda, tax, nop, ldy, lda, ldx, nop, /* A */
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/* B */ bcs, lda, nop, lax, ldy, lda, ldx, lax, clv, lda, tsx, lax, ldy, lda, ldx, lax, /* B */
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/* B */ bcs, lda, nop, nop, ldy, lda, ldx, nop, clv, lda, tsx, nop, ldy, lda, ldx, nop, /* B */
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/* C */ cpy, cmp, nop, dcp, cpy, cmp, dec, dcp, iny, cmp, dex, nop, cpy, cmp, dec, dcp, /* C */
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/* C */ cpy, cmp, nop, nop, cpy, cmp, dec, nop, iny, cmp, dex, nop, cpy, cmp, dec, nop, /* C */
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/* D */ bne, cmp, nop, dcp, nop, cmp, dec, dcp, cld, cmp, nop, dcp, nop, cmp, dec, dcp, /* D */
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/* D */ bne, cmp, nop, nop, nop, cmp, dec, nop, cld, cmp, nop, nop, nop, cmp, dec, nop, /* D */
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/* E */ cpx, sbc, nop, isb, cpx, sbc, inc, isb, inx, sbc, nop, sbc, cpx, sbc, inc, isb, /* E */
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/* E */ cpx, sbc, nop, nop, cpx, sbc, inc, nop, inx, sbc, nop, sbc, cpx, sbc, inc, nop, /* E */
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/* F */ beq, sbc, nop, isb, nop, sbc, inc, isb, sed, sbc, nop, isb, nop, sbc, inc, isb /* F */
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/* F */ beq, sbc, nop, nop, nop, sbc, inc, nop, sed, sbc, nop, nop, nop, sbc, inc, nop /* F */
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};
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};
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static const uint32_t ticktable[256] = {
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static const uint32_t ticktable[256] = {
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@ -835,8 +741,6 @@ void exec6502(uint32_t tickcount) {
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clockticks6502 += ticktable[opcode];
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clockticks6502 += ticktable[opcode];
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if (penaltyop && penaltyaddr) clockticks6502++;
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if (penaltyop && penaltyaddr) clockticks6502++;
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instructions++;
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if (callexternal) (*loopexternal)();
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if (callexternal) (*loopexternal)();
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}
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}
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@ -854,8 +758,6 @@ void step6502() {
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if (penaltyop && penaltyaddr) clockticks6502++;
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if (penaltyop && penaltyaddr) clockticks6502++;
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clockgoal6502 = clockticks6502;
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clockgoal6502 = clockticks6502;
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instructions++;
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if (callexternal) (*loopexternal)();
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if (callexternal) (*loopexternal)();
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}
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}
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