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Not complete, but this gets large chunks of the MC6809 addition and subtraction parts of the emulator working correctly

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Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2018-10-14 20:40:20 +01:00
parent 337e35ca1b
commit 707a742899
2 changed files with 11 additions and 17 deletions
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14
MC6809/inc/mc6809.h
View File

@ -206,11 +206,11 @@ namespace EightBit {
void adjustBorrow(register16_t datum) { adjustBorrow(datum.word); }
void adjustOverflow(uint8_t before, uint8_t data, uint8_t after) {
setFlag(CC(), VF, !!((before ^ data ^ after ^ (after >> 1)) & Bit7));
setFlag(CC(), VF, ~(before ^ data) & (before ^ after) & Bit7);
}
void adjustOverflow(uint16_t before, uint16_t data, uint16_t after) {
setFlag(CC(), VF, !!((before ^ data ^ after ^ (after >> 1)) & Bit15));
setFlag(CC(), VF, ~(before ^ data) & (before ^ after) & Bit15);
}
void adjustOverflow(register16_t before, register16_t data, register16_t after) {
@ -243,14 +243,14 @@ namespace EightBit {
void adjustSubtraction(uint8_t before, uint8_t data, register16_t after) {
const auto result = after.low;
adjustNZ(result);
adjustBorrow(after);
adjustOverflow(before, data, result);
adjustCarry(after);
setFlag(CC(), VF, (before ^ data ^ result ^ (after.high << 7)) & Bit7);
}
void adjustSubtraction(uint16_t before, uint16_t data, uint32_t after) {
const register16_t result = after & Mask16;
adjustNZ(result);
adjustBorrow(after);
adjustCarry(after);
adjustOverflow(before, data, result);
}
@ -300,7 +300,7 @@ namespace EightBit {
// Instruction implementations
uint8_t adc(uint8_t operand, uint8_t data);
uint8_t add(uint8_t operand, uint8_t data, int carry = 0);
uint8_t add(uint8_t operand, uint8_t data, uint8_t carry = 0);
register16_t add(register16_t operand, register16_t data);
uint8_t andr(uint8_t operand, uint8_t data);
uint8_t asl(uint8_t operand);
@ -329,7 +329,7 @@ namespace EightBit {
void rti();
void rts();
uint8_t sbc(uint8_t operand, uint8_t data);
uint8_t sub(uint8_t operand, uint8_t data, int carry = 0);
uint8_t sub(uint8_t operand, uint8_t data, uint8_t carry = 0);
register16_t sub(register16_t operand, register16_t data);
uint8_t sex(uint8_t from);
void swi();

14
MC6809/src/mc6809.cpp
View File

@ -756,7 +756,7 @@ uint8_t EightBit::mc6809::adc(const uint8_t operand, const uint8_t data) {
return add(operand, data, carry());
}
uint8_t EightBit::mc6809::add(const uint8_t operand, const uint8_t data, const int carry) {
uint8_t EightBit::mc6809::add(const uint8_t operand, const uint8_t data, const uint8_t carry) {
const register16_t addition = operand + data + carry;
adjustAddition(operand, data, addition);
return addition.low;
@ -837,10 +837,7 @@ uint8_t EightBit::mc6809::da(uint8_t operand) {
}
uint8_t EightBit::mc6809::dec(const uint8_t operand) {
const uint8_t result = operand - 1;
adjustNZ(result);
adjustOverflow(operand, 1, result);
return result;
return sub(operand, 1);
}
uint8_t EightBit::mc6809::eor(uint8_t operand, const uint8_t data) {
@ -898,10 +895,7 @@ void EightBit::mc6809::exg(const uint8_t data) {
}
uint8_t EightBit::mc6809::inc(uint8_t operand) {
const uint8_t result = operand + 1;
adjustNZ(result);
adjustOverflow(operand, 1, result);
return result;
return add(operand, 1);
}
void EightBit::mc6809::jsr(const register16_t address) {
@ -1109,7 +1103,7 @@ uint8_t EightBit::mc6809::sbc(const uint8_t operand, const uint8_t data) {
return sub(operand, data, carry());
}
uint8_t EightBit::mc6809::sub(const uint8_t operand, const uint8_t data, const int carry) {
uint8_t EightBit::mc6809::sub(const uint8_t operand, const uint8_t data, const uint8_t carry) {
const register16_t subtraction = operand - data - carry;
adjustSubtraction(operand, data, subtraction);
return subtraction.low;