Fix some instructions, add missing ones
Get cpu6502 to pass functional tests from https://github.com/Klaus2m5/6502_65C02_functional_tests Set bit 5 on status register pushed during IRQ, NMI, BRK. Fix return address pushed for BRK Fix flag setting for ROR Fix flags pushed with PHP Fix return address for RTI Add 0xD5 - DEC zpg, X Add 0xE1 - SBC (ind, X) Add 0x61 - ADC (ind, X) Add 0x1E - ASL abs, x Add 0x21 - AND (ind, X) Add 0x96 - STX zpg, Y add 0x75 - ADC zpg, X
This commit is contained in:
Brad Grantham
parent
bbe1934dec
commit
1d8f0e0564
121
cpu6502.h
121
cpu6502.h
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@ -11,7 +11,7 @@
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BUS template parameter must provide methods:
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uint8_t read(uint16_t addr);
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void read(uint16_t addr, uint8_t data);
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void write(uint16_t addr, uint8_t data);
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*/
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/*
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@ -38,6 +38,7 @@ struct CPU6502
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static constexpr uint8_t N = 0x80;
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static constexpr uint8_t V = 0x40;
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static constexpr uint8_t B2 = 0x20;
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static constexpr uint8_t B = 0x10;
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static constexpr uint8_t D = 0x08;
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static constexpr uint8_t I = 0x04;
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@ -165,7 +166,7 @@ struct CPU6502
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{
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stack_push((pc - 1) >> 8);
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stack_push((pc - 1) & 0xFF);
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stack_push(p);
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stack_push(p | B2);
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uint8_t low = bus.read(0xFFFE);
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uint8_t high = bus.read(0xFFFF);
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pc = low + high * 256;
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@ -176,7 +177,7 @@ struct CPU6502
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{
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stack_push((pc - 1) >> 8);
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stack_push((pc - 1) & 0xFF);
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stack_push(p);
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stack_push(p | B2);
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uint8_t low = bus.read(0xFFFA);
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uint8_t high = bus.read(0xFFFB);
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pc = low + high * 256;
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@ -200,9 +201,10 @@ struct CPU6502
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switch(inst) {
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case 0x00: { // BRK
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stack_push((pc - 1) >> 8);
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stack_push((pc - 1) & 0xFF);
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stack_push(p | B); // | B says the Synertek 6502 reference
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stack_push((pc + 1) >> 8);
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stack_push((pc + 1) & 0xFF);
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stack_push(p | B2 | B); // | B says the Synertek 6502 reference
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p |= I;
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uint8_t low = bus.read(0xFFFE);
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uint8_t high = bus.read(0xFFFF);
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pc = low + high * 256;
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@ -286,6 +288,13 @@ struct CPU6502
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break;
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}
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case 0xD6: { // DEC zpg, X
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uint8_t zpg = (read_pc_inc() + x) % 0xFF;
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set_flags(N | Z, m = bus.read(zpg) - 1);
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bus.write(zpg, m);
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break;
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}
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case 0xDE: { // DEC abs, X
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uint8_t low = read_pc_inc();
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uint8_t high = read_pc_inc();
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@ -576,6 +585,29 @@ struct CPU6502
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break;
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}
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case 0xE1: { // SBC ind, X
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uint8_t zpg = (read_pc_inc() + x) & 0xFF;
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uint8_t low = bus.read(zpg);
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uint8_t high = bus.read((zpg + 1) & 0xFF);
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uint16_t addr = low + high * 256;
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if((addr - y) / 256 != addr / 256)
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clk.add_cpu_cycles(1);
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m = bus.read(addr);
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uint8_t borrow = isset(C) ? 0 : 1;
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if(isset(D)) {
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uint8_t bcd = a / 16 * 10 + a % 16;
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flag_change(C, !(bcd < m + borrow));
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flag_change(V, sbc_overflow_d(bcd, m, borrow));
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set_flags(N | Z, bcd = bcd - (m + borrow));
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a = bcd / 10 * 16 + bcd % 10;
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} else {
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flag_change(C, !(a < (m + borrow)));
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flag_change(V, sbc_overflow(a, m, borrow));
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set_flags(N | Z, a = a - (m + borrow));
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}
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break;
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}
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case 0xF1: { // SBC ind, Y
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uint8_t zpg = read_pc_inc();
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uint8_t low = bus.read(zpg);
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@ -703,6 +735,29 @@ struct CPU6502
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break;
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}
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case 0x61: { // ADC (ind, X)
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uint8_t zpg = (read_pc_inc() + x) & 0xFF;
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uint8_t low = bus.read(zpg);
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uint8_t high = bus.read((zpg + 1) & 0xFF);
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uint16_t addr = low + high * 256;
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if((addr - y) / 256 != addr / 256)
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clk.add_cpu_cycles(1);
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m = bus.read(addr);
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uint8_t carry = isset(C) ? 1 : 0;
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if(isset(D)) {
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uint8_t bcd = a / 16 * 10 + a % 16;
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flag_change(C, ((uint16_t)bcd + (uint16_t)m + carry) > 99);
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flag_change(V, adc_overflow_d(bcd, m, carry));
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set_flags(N | Z, bcd = bcd + m + carry);
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a = bcd / 10 * 16 + bcd % 10;
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} else {
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flag_change(C, ((uint16_t)a + (uint16_t)m + carry) > 0xFF);
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flag_change(V, adc_overflow(a, m, carry));
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set_flags(N | Z, a = a + m + carry);
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}
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break;
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}
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case 0x6D: { // ADC abs
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uint8_t low = read_pc_inc();
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uint8_t high = read_pc_inc();
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@ -811,6 +866,15 @@ struct CPU6502
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break;
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}
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case 0x1E: { // ASL abs
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uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
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m = bus.read(addr + x);
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flag_change(C, m & 0x80);
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set_flags(N | Z, m = m << 1);
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bus.write(addr + x, m);
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break;
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}
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case 0x06: { // ASL
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uint8_t zpg = read_pc_inc();
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m = bus.read(zpg);
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@ -970,6 +1034,17 @@ struct CPU6502
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break;
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}
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case 0x21: { // AND (ind, X)
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uint8_t zpg = (read_pc_inc() + x) & 0xFF;
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uint8_t low = bus.read(zpg);
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uint8_t high = bus.read((zpg + 1) & 0xFF);
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uint16_t addr = low + high * 256;
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if((addr - y) / 256 != addr / 256)
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clk.add_cpu_cycles(1);
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set_flags(N | Z, a = a & bus.read(addr));
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break;
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}
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case 0x31: { // AND (ind), y
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uint8_t zpg = read_pc_inc();
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uint8_t low = bus.read(zpg);
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@ -1032,7 +1107,7 @@ struct CPU6502
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uint16_t addr = low + high * 256;
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m = bus.read(addr + x);
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bool c = isset(C);
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flag_change(C, m & 0x80);
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flag_change(C, m & 0x01);
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set_flags(N | Z, m = (c ? 0x80 : 0x00) | (m >> 1));
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bus.write(addr + x, m);
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break;
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@ -1042,7 +1117,7 @@ struct CPU6502
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uint8_t zpg = (read_pc_inc() + x) & 0xFF;
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m = bus.read(zpg);
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bool c = isset(C);
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flag_change(C, m & 0x01);
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flag_change(C, m & 0x80);
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set_flags(N | Z, m = (c ? 0x01 : 0x00) | (m << 1));
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bus.write(zpg, m);
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break;
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@ -1192,7 +1267,7 @@ struct CPU6502
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}
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case 0x08: { // PHP
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stack_push(p);
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stack_push(p | B2 | B);
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break;
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}
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@ -1475,7 +1550,7 @@ struct CPU6502
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p = stack_pull();
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uint8_t pcl = stack_pull();
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uint8_t pch = stack_pull();
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pc = pcl + pch * 256 + 1;
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pc = pcl + pch * 256;
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break;
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}
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@ -1512,6 +1587,13 @@ struct CPU6502
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break;
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}
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case 0x96: { // STX zpg, Y
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uint8_t zpg = read_pc_inc();
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uint16_t addr = (zpg + y) & 0xFF;
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bus.write(addr, x);
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break;
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}
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case 0x84: { // STY
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uint8_t zpg = read_pc_inc();
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bus.write(zpg, y);
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@ -1605,6 +1687,25 @@ struct CPU6502
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break;
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}
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case 0x75: { // ADC zpg, X
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uint8_t zpg = read_pc_inc();
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uint16_t addr = (zpg + x)& 0xFF;
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m = bus.read(addr);
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uint8_t carry = isset(C) ? 1 : 0;
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if(isset(D)) {
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uint8_t bcd = a / 16 * 10 + a % 16;
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flag_change(C, ((uint16_t)bcd + (uint16_t)m + carry) > 99);
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flag_change(V, adc_overflow_d(bcd, m, carry));
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set_flags(N | Z, bcd = bcd + m + carry);
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a = bcd / 10 * 16 + bcd % 10;
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} else {
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flag_change(C, ((uint16_t)a + (uint16_t)m + carry) > 0xFF);
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flag_change(V, adc_overflow(a, m, carry));
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set_flags(N | Z, a = a + m + carry);
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}
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break;
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}
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case 0x3A: { // DEC, 65C02
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set_flags(N | Z, a = a - 1);
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break;
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