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make ordering explicit of some 16-bit addressing

This commit is contained in:
Brad Grantham 2020-12-16 17:29:37 -08:00
parent c2eb84b38c
commit fb7d31d814
1 changed files with 208 additions and 71 deletions
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279
cpu6502.h
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@ -155,7 +155,9 @@ struct CPU6502
void reset()
{
s = 0xFD;
pc = bus.read(0xFFFC) + bus.read(0xFFFD) * 256;
uint8_t low = bus.read(0xFFFC);
uint8_t high = bus.read(0xFFFD);
pc = low + high * 256;
exception = NONE;
}
@ -164,7 +166,9 @@ struct CPU6502
stack_push((pc - 1) >> 8);
stack_push((pc - 1) & 0xFF);
stack_push(p);
pc = bus.read(0xFFFE) + bus.read(0xFFFF) * 256;
uint8_t low = bus.read(0xFFFE);
uint8_t high = bus.read(0xFFFF);
pc = low + high * 256;
exception = NONE;
}
@ -173,7 +177,9 @@ struct CPU6502
stack_push((pc - 1) >> 8);
stack_push((pc - 1) & 0xFF);
stack_push(p);
pc = bus.read(0xFFFA) + bus.read(0xFFFB) * 256;
uint8_t low = bus.read(0xFFFA);
uint8_t high = bus.read(0xFFFB);
pc = low + high * 256;
exception = NONE;
}
@ -197,7 +203,9 @@ struct CPU6502
stack_push((pc - 1) >> 8);
stack_push((pc - 1) & 0xFF);
stack_push(p | B); // | B says the Synertek 6502 reference
pc = bus.read(0xFFFE) + bus.read(0xFFFF) * 256;
uint8_t low = bus.read(0xFFFE);
uint8_t high = bus.read(0xFFFF);
pc = low + high * 256;
exception = NONE;
break;
}
@ -279,14 +287,18 @@ struct CPU6502
}
case 0xDE: { // DEC abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256 + x;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256 + x;
set_flags(N | Z, m = bus.read(addr) - 1);
bus.write(addr, m);
break;
}
case 0xCE: { // DEC abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
set_flags(N | Z, m = bus.read(addr) - 1);
bus.write(addr, m);
break;
@ -298,7 +310,9 @@ struct CPU6502
}
case 0xFE: { // INC abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256 + x;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256 + x;
if((addr - x) / 256 != addr / 256)
clk.add_cpu_cycles(1);
set_flags(N | Z, m = bus.read(addr) + 1);
@ -307,7 +321,9 @@ struct CPU6502
}
case 0xEE: { // INC abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
set_flags(N | Z, m = bus.read(addr) + 1);
bus.write(addr, m);
break;
@ -428,7 +444,9 @@ struct CPU6502
case 0xA1: { // LDA (ind, X)
uint8_t zpg = (read_pc_inc() + x) & 0xFF;
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256;
set_flags(N | Z, a = bus.read(addr));
break;
}
@ -442,7 +460,9 @@ struct CPU6502
case 0xB1: { // LDA ind, Y
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256 + y;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256 + y;
if((addr - y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
set_flags(N | Z, a = bus.read(addr));
@ -456,7 +476,9 @@ struct CPU6502
}
case 0xDD: { // CMP abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr + x);
if((addr + x) / 256 != addr / 256)
clk.add_cpu_cycles(1);
@ -467,7 +489,9 @@ struct CPU6502
case 0xC1: { // CMP (ind, X)
uint8_t zpg = (read_pc_inc() + x) & 0xFF;
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256;
m = bus.read(addr);
flag_change(C, m <= a);
set_flags(N | Z, m = a - m);
@ -475,7 +499,9 @@ struct CPU6502
}
case 0xD9: { // CMP abs, Y
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr + y);
if((addr + y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
@ -485,7 +511,9 @@ struct CPU6502
}
case 0xB9: { // LDA abs, Y
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
set_flags(N | Z, a = bus.read(addr + y));
if((addr + y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
@ -493,7 +521,9 @@ struct CPU6502
}
case 0xBC: { // LDY abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
set_flags(N | Z, y = bus.read(addr + x));
if((addr + x) / 256 != addr / 256)
clk.add_cpu_cycles(1);
@ -501,7 +531,9 @@ struct CPU6502
}
case 0xBD: { // LDA abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
set_flags(N | Z, a = bus.read(addr + x));
if((addr + x) / 256 != addr / 256)
clk.add_cpu_cycles(1);
@ -546,7 +578,9 @@ struct CPU6502
case 0xF1: { // SBC ind, Y
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xff) * 256 + y;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256 + y;
if((addr - y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
m = bus.read(addr);
@ -566,7 +600,9 @@ struct CPU6502
}
case 0xF9: { // SBC abs, Y
uint16_t addr = read_pc_inc() + read_pc_inc() * 256 + y;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256 + y;
if((addr - y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
uint8_t m = bus.read(addr);
@ -586,7 +622,9 @@ struct CPU6502
}
case 0xFD: { // SBC abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256 + x;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256 + x;
if((addr - x) / 256 != addr / 256)
clk.add_cpu_cycles(1);
uint8_t m = bus.read(addr);
@ -606,7 +644,9 @@ struct CPU6502
}
case 0xED: { // SBC abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
uint8_t m = bus.read(addr);
uint8_t borrow = isset(C) ? 0 : 1;
if(isset(D)) {
@ -642,7 +682,9 @@ struct CPU6502
case 0x71: { // ADC (ind), Y
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256 + y;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256 + y;
if((addr - y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
m = bus.read(addr);
@ -662,7 +704,9 @@ struct CPU6502
}
case 0x6D: { // ADC abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr);
uint8_t carry = isset(C) ? 1 : 0;
if(isset(D)) {
@ -698,7 +742,9 @@ struct CPU6502
}
case 0x7D: { // ADC abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256 + x;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256 + x;
if((addr - x) / 256 != addr / 256)
clk.add_cpu_cycles(1);
m = bus.read(addr);
@ -718,7 +764,9 @@ struct CPU6502
}
case 0x79: { // ADC abs, Y
uint16_t addr = read_pc_inc() + read_pc_inc() * 256 + y;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256 + y;
if((addr - y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
m = bus.read(addr);
@ -788,7 +836,9 @@ struct CPU6502
}
case 0x5E: { // LSR abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr + x);
flag_change(C, m & 0x01);
set_flags(N | Z, m = m >> 1);
@ -815,7 +865,9 @@ struct CPU6502
}
case 0x4E: { // LSR
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr);
flag_change(C, m & 0x01);
set_flags(N | Z, m = m >> 1);
@ -841,7 +893,9 @@ struct CPU6502
case 0x01: { // ORA (ind, X)
uint8_t zpg = (read_pc_inc() + x) & 0xFF;
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256;
m = bus.read(addr);
set_flags(N | Z, a = a | m);
break;
@ -855,14 +909,18 @@ struct CPU6502
}
case 0x0D: { // ORA abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr);
set_flags(N | Z, a = a | m);
break;
}
case 0x19: { // ORA abs, Y
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr + y);
if((addr + y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
@ -871,7 +929,9 @@ struct CPU6502
}
case 0x1D: { // ORA abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr + x);
if((addr + x) / 256 != addr / 256)
clk.add_cpu_cycles(1);
@ -881,7 +941,9 @@ struct CPU6502
case 0x11: { // ORA (ind), Y
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256 + y;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256 + y;
if((addr - y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
m = bus.read(addr);
@ -910,7 +972,9 @@ struct CPU6502
case 0x31: { // AND (ind), y
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256 + y;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256 + y;
if((addr - y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
set_flags(N | Z, a = a & bus.read(addr));
@ -918,7 +982,9 @@ struct CPU6502
}
case 0x3D: { // AND abs, x
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
set_flags(N | Z, a = a & bus.read(addr + x));
if((addr + x) / 256 != addr / 256)
clk.add_cpu_cycles(1);
@ -926,7 +992,9 @@ struct CPU6502
}
case 0x39: { // AND abs, y
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
set_flags(N | Z, a = a & bus.read(addr + y));
if((addr + y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
@ -934,7 +1002,9 @@ struct CPU6502
}
case 0x2D: { // AND abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
set_flags(N | Z, a = a & bus.read(addr));
break;
}
@ -957,7 +1027,9 @@ struct CPU6502
}
case 0x7E: { // ROR abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr + x);
bool c = isset(C);
flag_change(C, m & 0x80);
@ -978,7 +1050,9 @@ struct CPU6502
case 0x3E: { // ROL abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr + x);
bool c = isset(C);
flag_change(C, m & 0x80);
@ -1002,7 +1076,9 @@ struct CPU6502
}
case 0x6E: { // ROR abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr);
bool c = isset(C);
flag_change(C, m & 0x01);
@ -1032,7 +1108,9 @@ struct CPU6502
}
case 0x2E: { // ROL abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr);
bool c = isset(C);
flag_change(C, m & 0x80);
@ -1053,13 +1131,17 @@ struct CPU6502
}
case 0x4C: { // JMP
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
pc = addr;
break;
}
case 0x6C: { // JMP
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
case 0x6C: { // JMP indirect
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
uint8_t addrl = bus.read(addr);
uint8_t addrh = bus.read(addr + 1);
addr = addrl + addrh * 256;
@ -1068,33 +1150,43 @@ struct CPU6502
}
case 0x9D: { // STA abs, x
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
bus.write(addr + x, a);
break;
}
case 0x99: { // STA
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
bus.write(addr + y, a);
break;
}
case 0x91: { // STA (ind), Y
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256 + y;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256 + y;
bus.write(addr, a);
break;
}
case 0x81: { // STA (ind, X)
uint8_t zpg = (read_pc_inc() + x) & 0xFF;
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256;
bus.write(addr, a);
break;
}
case 0x8D: { // STA
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
bus.write(addr, a);
break;
}
@ -1119,7 +1211,9 @@ struct CPU6502
}
case 0x2C: { // BIT
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr);
flag_change(Z, (a & m) == 0);
flag_change(N, m & 0x80);
@ -1134,13 +1228,17 @@ struct CPU6502
}
case 0xAE: { // LDX abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
set_flags(N | Z, x = bus.read(addr));
break;
}
case 0xBE: { // LDX
uint16_t addr = read_pc_inc() + read_pc_inc() * 256 + y;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256 + y;
if((addr - y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
set_flags(N | Z, x = bus.read(addr));
@ -1166,7 +1264,9 @@ struct CPU6502
}
case 0xAC: { // LDY
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
set_flags(N | Z, y = bus.read(addr));
break;
}
@ -1190,13 +1290,17 @@ struct CPU6502
}
case 0xAD: { // LDA
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
set_flags(N | Z, a = bus.read(addr));
break;
}
case 0xCC: { // CPY abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr);
flag_change(C, m <= y);
set_flags(N | Z, m = y - m);
@ -1204,7 +1308,9 @@ struct CPU6502
}
case 0xEC: { // CPX abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr);
flag_change(C, m <= x);
set_flags(N | Z, m = x - m);
@ -1234,21 +1340,27 @@ struct CPU6502
case 0x41: { // EOR (ind, X)
uint8_t zpg = (read_pc_inc() + x) & 0xFF;
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256;
m = bus.read(addr);
set_flags(N | Z, a = a ^ m);
break;
}
case 0x4D: { // EOR abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr);
set_flags(N | Z, a = a ^ m);
break;
}
case 0x5D: { // EOR abs, X
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr + x);
if((addr + x) / 256 != addr / 256)
clk.add_cpu_cycles(1);
@ -1257,7 +1369,9 @@ struct CPU6502
}
case 0x59: { // EOR abs, Y
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr + y);
if((addr + y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
@ -1279,7 +1393,9 @@ struct CPU6502
case 0x51: { // EOR
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256 + y;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256 + y;
if((addr - y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
m = bus.read(addr);
@ -1289,7 +1405,9 @@ struct CPU6502
case 0xD1: { // CMP
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256 + y;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256 + y;
if((addr - y) / 256 != addr / 256)
clk.add_cpu_cycles(1);
m = bus.read(addr);
@ -1307,7 +1425,9 @@ struct CPU6502
}
case 0xCD: { // CMP
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
m = bus.read(addr);
flag_change(C, m <= a);
set_flags(N | Z, m = a - m);
@ -1379,7 +1499,9 @@ struct CPU6502
}
case 0x8E: { // STX abs
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
bus.write(addr, x);
break;
}
@ -1397,7 +1519,9 @@ struct CPU6502
}
case 0x8C: { // STY
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
bus.write(addr, y);
break;
}
@ -1405,7 +1529,9 @@ struct CPU6502
case 0x20: { // JSR
stack_push((pc + 1) >> 8);
stack_push((pc + 1) & 0xFF);
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
pc = addr;
break;
}
@ -1428,7 +1554,9 @@ struct CPU6502
}
case 0x9C: { // STZ abs, 65C02
uint16_t addr = read_pc_inc() + read_pc_inc() * 256;
uint8_t low = read_pc_inc();
uint8_t high = read_pc_inc();
uint16_t addr = low + high * 256;
bus.write(addr, 0x0);
break;
}
@ -1440,22 +1568,27 @@ struct CPU6502
case 0xB2: { // LDA (zpg), 65C02
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256;
set_flags(N | Z, a = bus.read(addr));
break;
}
case 0x92: { // STA (zpg), 65C02
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256;
bus.write(addr, a);
break;
}
case 0x72: { // ADC (zpg), 65C02
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256;
m = bus.read(addr);
uint8_t carry = isset(C) ? 1 : 0;
if(isset(D)) {
@ -1484,7 +1617,9 @@ struct CPU6502
case 0x12: { // ORA (ind), 65C02
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256;
m = bus.read(addr);
set_flags(N | Z, a = a | m);
break;
@ -1492,7 +1627,9 @@ struct CPU6502
case 0xD2: { // CMP (zpg), 65C02 instruction
uint8_t zpg = read_pc_inc();
uint16_t addr = bus.read(zpg) + bus.read((zpg + 1) & 0xFF) * 256;
uint8_t low = bus.read(zpg);
uint8_t high = bus.read((zpg + 1) & 0xFF);
uint16_t addr = low + high * 256;
m = bus.read(addr);
flag_change(C, m <= a);
set_flags(N | Z, m = a - m);