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Easier to read flag handling in the 6809

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Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2018-08-24 12:30:16 +01:00
parent 21e8360dc1
commit adb6433737
2 changed files with 15 additions and 14 deletions
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1
MC6809/inc/mc6809.h
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@ -235,6 +235,7 @@ namespace EightBit {
int zero() { return CC() & ZF; }
int overflow() { return CC() & VF; }
int carry() { return CC() & CF; }
int halfCarry() { return CC() & HF; }
bool BLS() { return carry() | (zero() >> 2); } // (C OR Z)
bool BHI() { return !BLS(); } // !(C OR Z)

28
MC6809/src/mc6809.cpp
View File

@ -31,7 +31,7 @@ int EightBit::mc6809::step() {
void EightBit::mc6809::reset() {
Processor::reset();
DP() = 0; // Reestablish zero page
CC() |= (IF & FF); // Disable IRQ and FIRQ
setFlag(CC(), IF | FF); // Disable IRQ and FIRQ
jump(getWordPaged(0xff, RESETvector));
}
@ -46,17 +46,17 @@ void EightBit::mc6809::handleIRQ() {
raise(IRQ());
addCycles(21);
saveEntireRegisterState();
CC() |= IF; // Disable IRQ
setFlag(CC(), IF); // Disable IRQ
jump(getWordPaged(0xff, IRQvector));
}
void EightBit::mc6809::handleFIRQ() {
addCycles(12);
raise(FIRQ());
CC() &= ~EF; // Clear the EF flag. i.e. this only saves PC and CC
clearFlag(CC(), EF); // Clear the EF flag. i.e. this only saves PC and CC
pushWordS(PC());
pushS(CC());
CC() |= (IF & FF); // Disable IRQ and FIRQ
setFlag(CC(), IF | FF); // Disable IRQ and FIRQ
jump(getWordPaged(0xff, FIRQvector));
}
@ -707,7 +707,7 @@ EightBit::register16_t EightBit::mc6809::AM_extended_word() {
//
void EightBit::mc6809::saveEntireRegisterState() {
CC() |= EF;
setFlag(CC(), EF); // Entire flag set saved
pushWordS(PC());
pushWordS(U());
pushWordS(Y());
@ -721,7 +721,7 @@ void EightBit::mc6809::saveEntireRegisterState() {
//
uint8_t EightBit::mc6809::adc(uint8_t operand, uint8_t data) {
return add(operand, data, CC() & CF);
return add(operand, data, carry());
}
uint8_t EightBit::mc6809::add(uint8_t operand, uint8_t data, int carry) {
@ -745,7 +745,7 @@ uint8_t EightBit::mc6809::andr(uint8_t operand, uint8_t data) {
uint8_t EightBit::mc6809::asl(uint8_t operand) {
setFlag(CC(), CF, operand & Bit7);
adjustNZ(operand <<= 1);
const auto overflow = (CC() & CF) ^ ((CC() & NF) >> 3);
const auto overflow = (carry() ^ (negative() >> 3);
setFlag(CC(), VF, overflow);
return operand;
}
@ -789,8 +789,8 @@ uint8_t EightBit::mc6809::da(uint8_t operand) {
clearFlag(CC(), VF);
setFlag(CC(), CF, A() > 0x99);
const auto lowAdjust = (CC() & HF) || (lowNibble(A()) > 9);
const auto highAdjust = (CC() & CF) || (A() > 0x99);
const auto lowAdjust = halfCarry() || (lowNibble(A()) > 9);
const auto highAdjust = carry() || (A() > 0x99);
if (lowAdjust)
A() += 6;
@ -1049,20 +1049,20 @@ void EightBit::mc6809::pulu(uint8_t data) {
}
uint8_t EightBit::mc6809::rol(uint8_t operand) {
const auto carry = CC() & CF;
const auto carryIn = carry();
setFlag(CC(), CF, operand & Bit7);
setFlag(CC(), VF, ((operand & Bit7) >> 7) ^ ((operand & Bit6) >> 6));
operand <<= 1;
operand |= carry;
operand |= carryIn;
adjustNZ(operand);
return operand;
}
uint8_t EightBit::mc6809::ror(uint8_t operand) {
const auto carry = CC() & CF;
const auto carryIn = carry();
setFlag(CC(), CF, operand & Bit0);
operand >>= 1;
operand |= (carry << 7);
operand |= (carryIn << 7);
adjustNZ(operand);
return operand;
}
@ -1134,7 +1134,7 @@ EightBit::register16_t EightBit::mc6809::st(register16_t data) {
}
uint8_t EightBit::mc6809::sbc(uint8_t operand, uint8_t data) {
return sub(operand, data, CC() & CF);
return sub(operand, data, carry());
}
uint8_t EightBit::mc6809::sub(uint8_t operand, uint8_t data, int carry) {