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[#201] z80-cpu: fixes
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@vbmacher
vbmacher committed Mar 17, 2022
1 parent 108baac commit 6498ff7
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Showing 6 changed files with 343 additions and 287 deletions.
159 changes: 119 additions & 40 deletions plugins/cpu/z80-cpu/src/main/java/net/emustudio/plugins/cpu/zilogZ80/EmulatorEngine.java
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Original file line number Diff line number Diff line change
Expand Up @@ -401,15 +401,33 @@ private void writeWord(int address, int value) {
memory.write(address, new Byte[]{(byte) (value & 0xFF), (byte) ((value >>> 8) & 0xFF)}, 2);
}

private int flagSZHPC(int a, int b, int sum) {
int carryOut = (a > 0xFF - b) ? FLAG_C : 0;
private int flagSZHPC(int a, int b, int flagC, int sum) {
// source: https://stackoverflow.com/questions/8034566/overflow-and-carry-flags-on-z80
int carryOut;
if (flagC == FLAG_C) {
carryOut = (a >= 0xFF - b) ? FLAG_C : 0;
} else {
carryOut = (a > 0xFF - b) ? FLAG_C : 0;
}

int carryIns = sum ^ a ^ b;
int halfCarryOut = (carryIns >> 4) & 1;
int overflowOut = (((carryIns >> 7) ^ carryOut) != 0) ? FLAG_PV : 0;

return carryOut | (halfCarryOut << 4) | (overflowOut) | (sum == 0 ? FLAG_Z : 0) | (sum & 0x80);
}

private int flagSZHP(int a, int b, int sum) {
// source: https://stackoverflow.com/questions/8034566/overflow-and-carry-flags-on-z80
int carryOut = (a > 0xFF - b) ? FLAG_C : 0;

int carryIns = sum ^ a ^ b;
int halfCarryOut = (carryIns >> 4) & 1;
int overflowOut = (((carryIns >> 7) ^ carryOut) != 0) ? FLAG_PV : 0;

return (halfCarryOut << 4) | (overflowOut) | (sum == 0 ? FLAG_Z : 0) | (sum & 0x80);
}

private void bigOverflow(int i, int j, int result) {
int sign = i & 0x8000;
if (sign != (j & 0x8000)) {
Expand Down Expand Up @@ -551,15 +569,15 @@ int I_LD_R_N() {
int I_INC_R() {
int reg = (lastOpcode >>> 3) & 0x07;
int value = (getreg(reg) + 1) & 0xFF;
flags = EmulatorTables.INC_TABLE[value] | (flags & FLAG_C);
flags = flagSZHP(getreg(reg), 1, value);
putreg(reg, value);
return (reg == 6) ? 11 : 4;
}

int I_DEC_R() {
int reg = (lastOpcode >>> 3) & 0x07;
int value = (getreg(reg) - 1) & 0xFF;
flags = EmulatorTables.DEC_TABLE[value] | (flags & FLAG_C);
flags = flagSZHP(getreg(reg), ((~1) + 1) & 0xFF, value) | FLAG_N;
putreg(reg, value);
return (reg == 6) ? 11 : 4;
}
Expand All @@ -585,31 +603,41 @@ int I_ADD_A_R() {
int value = getreg(lastOpcode & 0x07);
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value) & 0xFF;
flags = flagSZHPC(oldA, value, regs[REG_A]);
flags = flagSZHPC(oldA, value, 0, regs[REG_A]);
return (lastOpcode == 0x86) ? 7 : 4;
}

int I_ADC_A_R() {
int value = getreg(lastOpcode & 0x07);
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value + (flags & FLAG_C)) & 0xFF;
flags = flagSZHPC(oldA, (value + (flags & FLAG_C)) & 0xFF, regs[REG_A]);
flags = flagSZHPC(oldA, value, (flags & FLAG_C), regs[REG_A]);
return (lastOpcode == 0x8E) ? 7 : 4;
}

int I_SUB_R() {
int value = ((~getreg(lastOpcode & 0x07)) + 1) & 0xFF;
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value) & 0xFF;
flags = flagSZHPC(oldA, value, regs[REG_A]) | FLAG_N;
flags = flagSZHPC(oldA, value, 0, regs[REG_A]) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return (lastOpcode == 0x96) ? 7 : 4;
}

int I_SBC_A_R() {
int value = ((~getreg(lastOpcode & 0x07)) + 1) & 0xFF;
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value - (flags & FLAG_C)) & 0xFF;
flags = flagSZHPC(oldA, (value - (flags & FLAG_C)) & 0xFF, regs[REG_A]) | FLAG_N;
flags = flagSZHPC(oldA, value, ((flags & FLAG_C) == FLAG_C) ? 0 : FLAG_C, regs[REG_A]) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return (lastOpcode == 0x9E) ? 7 : 4;
}

Expand All @@ -634,7 +662,12 @@ int I_OR_R() {
int I_CP_R() {
int value = ((~getreg(lastOpcode & 7)) + 1) & 0xFF;
int result = (regs[REG_A] + value) & 0xFF;
flags = flagSZHPC(regs[REG_A], value, result) | FLAG_N;
flags = flagSZHPC(regs[REG_A], value, 0, result) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return (lastOpcode == 0xBE) ? 7 : 4;
}

Expand Down Expand Up @@ -1373,7 +1406,7 @@ int I_ADD_A_N() {
PC = (PC + 1) & 0xFFFF;
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value) & 0xFF;
flags = flagSZHPC(oldA, value, regs[REG_A]);
flags = flagSZHPC(oldA, value, 0, regs[REG_A]);
return 7;
}

Expand All @@ -1382,7 +1415,7 @@ int I_ADC_A_N() {
PC = (PC + 1) & 0xFFFF;
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value + (flags & FLAG_C)) & 0xFF;
flags = flagSZHPC(oldA, (value + (flags & FLAG_C)) & 0xFF, regs[REG_A]);
flags = flagSZHPC(oldA, value, flags & FLAG_C, regs[REG_A]);
return 7;
}

Expand All @@ -1398,7 +1431,12 @@ int I_SUB_N() {
PC = (PC + 1) & 0xFFFF;
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value) & 0xFF;
flags = flagSZHPC(oldA, value, regs[REG_A]) | FLAG_N;
flags = flagSZHPC(oldA, value, 0, regs[REG_A]) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return 7;
}

Expand All @@ -1414,7 +1452,12 @@ int I_SBC_A_N() {
PC = (PC + 1) & 0xFFFF;
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value - (flags & FLAG_C)) & 0xFF;
flags = flagSZHPC(oldA, (value - (flags & FLAG_C)) & 0xFF, regs[REG_A]) | FLAG_N;
flags = flagSZHPC(oldA, value, (flags & FLAG_C) == FLAG_C ? 0 : FLAG_C, regs[REG_A]) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return 7;
}

Expand Down Expand Up @@ -1449,7 +1492,12 @@ int I_CP_N() {
int value = ((~readByte(PC)) + 1) & 0xFF;
PC = (PC + 1) & 0xFFFF;
int diff = (regs[REG_A] + value) & 0xFF;
flags = flagSZHPC(regs[REG_A], value, diff) | FLAG_N;
flags = flagSZHPC(regs[REG_A], value, 0, diff) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return 7;
}

Expand Down Expand Up @@ -1836,13 +1884,13 @@ int I_INC_REF_IY_N() {
}

int I_INC_REF_II_N(int special) {
byte tmp = memory.read(PC);
byte disp = memory.read(PC);
PC = (PC + 1) & 0xFFFF;
int tmp1 = (special + tmp) & 0xFFFF;
int tmp2 = (memory.read(tmp1) + 1) & 0xFF;

memory.write(tmp1, (byte) tmp2);
flags = EmulatorTables.INC_TABLE[tmp2] | (flags & FLAG_C);
int address = (special + disp) & 0xFFFF;
int value = readByte(address);
int result = (value + 1) & 0xFF;
memory.write(address, (byte) result);
flags = flagSZHP(value, 1, result);
return 23;
}

Expand All @@ -1855,12 +1903,13 @@ int I_DEC_REF_IY_N() {
}

int I_DEC_REF_II_N(int special) {
int tmp = readByte(PC);
int disp = readByte(PC);
PC = (PC + 1) & 0xFFFF;
int tmp1 = (special + (byte) tmp) & 0xFFFF;
int tmp2 = (memory.read(tmp1) - 1) & 0xFF;
memory.write(tmp1, (byte) tmp2);
flags = EmulatorTables.DEC_TABLE[tmp2] | (flags & FLAG_C);
int address = (special + (byte) disp) & 0xFFFF;
int value = readByte(address);
int result = (value - 1) & 0xFF;
memory.write(address, (byte) result);
flags = flagSZHP(value, ((~1) + 1) & 0xFF, result) | FLAG_N;
return 23;
}

Expand Down Expand Up @@ -1926,7 +1975,7 @@ int I_ADD_A_REF_II_N(int special) {
int value = readByte((special + offset) & 0xFFFF);
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value) & 0xFF;
flags = flagSZHPC(oldA, value, regs[REG_A]);
flags = flagSZHPC(oldA, value, 0, regs[REG_A]);
return 19;
}

Expand All @@ -1944,7 +1993,7 @@ int I_ADC_A_REF_II_N(int special) {
int value = readByte((special + offset) & 0xFFFF);
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value + (flags & FLAG_C)) & 0xFF;
flags = flagSZHPC(oldA, (value + (flags & FLAG_C)) & 0xFF, regs[REG_A]);
flags = flagSZHPC(oldA, value, flags & FLAG_C, regs[REG_A]);
return 19;
}

Expand All @@ -1962,7 +2011,12 @@ int I_SUB_REF_II_N(int special) {
int value = ((~readByte((special + offset) & 0xFFFF)) + 1) & 0xFF;
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value) & 0xFF;
flags = flagSZHPC(oldA, value, regs[REG_A]) | FLAG_N;
flags = flagSZHPC(oldA, value, 0, regs[REG_A]) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return 19;
}

Expand All @@ -1980,7 +2034,12 @@ int I_SBC_A_REF_II_N(int special) {
int value = ((~readByte((special + offset) & 0xFFFF)) + 1) & 0xFF;
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value - (flags & FLAG_C)) & 0xFF;
flags = flagSZHPC(oldA, (value - (flags & FLAG_C)) & 0xFF, regs[REG_A]) | FLAG_N;
flags = flagSZHPC(oldA, value, ((flags & FLAG_C) == FLAG_C) ? 0 : FLAG_C, regs[REG_A]) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return 19;
}

Expand Down Expand Up @@ -2050,7 +2109,12 @@ int I_CP_REF_II_N(int special) {
PC = (PC + 1) & 0xFFFF;
int value = ((~readByte((special + offset) & 0xFFFF)) + 1) & 0xFF;
int diff = (regs[REG_A] + value) & 0xFF;
flags = flagSZHPC(regs[REG_A], value, diff) | FLAG_N;
flags = flagSZHPC(regs[REG_A], value, 0, diff) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return 19;
}

Expand Down Expand Up @@ -2369,9 +2433,9 @@ int I_INC_IYL() {
}

int I_INC(int value) {
int valueInc = (value + 1) & 0xFF;
flags = EmulatorTables.INC_TABLE[valueInc] | (flags & FLAG_C);
return valueInc;
int result = (value + 1) & 0xFF;
flags = flagSZHP(value, 1, result);
return result;
}

int I_DEC_IXH() {
Expand All @@ -2387,7 +2451,7 @@ int I_DEC_IYH() {
int I_DEC_IIH(int special) {
int reg = special >>> 8;
int value = (reg - 1) & 0xFF;
flags = EmulatorTables.DEC_TABLE[value] | (flags & FLAG_C);
flags = flagSZHP(reg, ((~1) + 1) & 0xFF, value) | FLAG_N;
return value;
}

Expand All @@ -2404,7 +2468,7 @@ int I_DEC_IYL() {
int I_DEC_IIL(int special) {
int reg = special & 0xFF;
int value = (reg - 1) & 0xFF;
flags = EmulatorTables.DEC_TABLE[value] | (flags & FLAG_C);
flags = flagSZHP(reg, ((~1) + 1) & 0xFF, value) | FLAG_N;
return value;
}

Expand Down Expand Up @@ -2531,7 +2595,7 @@ int I_ADD_A_IYL() {
int I_ADD_A(int value) {
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value) & 0xFF;
flags = flagSZHPC(oldA, value, regs[REG_A]);
flags = flagSZHPC(oldA, value, 0, regs[REG_A]);
return 8;
}

Expand All @@ -2554,7 +2618,7 @@ int I_ADC_A_IYL() {
int I_ADC_A(int value) {
int oldA = regs[REG_A];
regs[REG_A] = (oldA + value + (flags & FLAG_C)) & 0xFF;
flags = flagSZHPC(oldA, (value + (flags & FLAG_C)) & 0xFF, regs[REG_A]);
flags = flagSZHPC(oldA, value, flags & FLAG_C, regs[REG_A]);
return 8;
}

Expand All @@ -2578,7 +2642,12 @@ int I_SUB(int value) {
int valueNeg = ((~value) + 1) & 0xFF;
int oldA = regs[REG_A];
regs[REG_A] = (oldA + valueNeg) & 0xFF;
flags = flagSZHPC(oldA, valueNeg, regs[REG_A]) | FLAG_N;
flags = flagSZHPC(oldA, valueNeg, 0, regs[REG_A]) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return 8;
}

Expand All @@ -2602,7 +2671,12 @@ int I_SBC_A(int value) {
int valueNeg = ((~value) + 1) & 0xFF;
int oldA = regs[REG_A];
regs[REG_A] = (oldA + valueNeg - (flags & FLAG_C)) & 0xFF;
flags = flagSZHPC(oldA, (valueNeg - (flags & FLAG_C)) & 0xFF, regs[REG_A]) | FLAG_N;
flags = flagSZHPC(oldA, valueNeg, ((flags & FLAG_C) == FLAG_C) ? 0 : FLAG_C, regs[REG_A]) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return 8;
}

Expand Down Expand Up @@ -2691,7 +2765,12 @@ int I_CP_IYL() {
int I_CP(int value) {
int valueNeg = ((~value) + 1) & 0xFF;
int result = (regs[REG_A] + valueNeg) & 0xFF;
flags = flagSZHPC(regs[REG_A], valueNeg, result) | FLAG_N;
flags = flagSZHPC(regs[REG_A], valueNeg, 0, result) | FLAG_N;
if ((flags & FLAG_C) == FLAG_C) {
flags &= 0xFE;
} else {
flags |= FLAG_C;
}
return 8;
}
}
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