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Add an implementation of ADC for the 6809

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Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2018-08-19 10:15:37 +01:00
parent 15e1258f40
commit a7835b943a
2 changed files with 29 additions and 1 deletions
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8
MC6809/inc/mc6809.h
View File

@ -176,6 +176,10 @@ namespace EightBit {
//
uint8_t AM_immediate() {
return fetchByte();
}
uint8_t AM_direct() {
Address_direct();
return BUS().read();
@ -187,13 +191,15 @@ namespace EightBit {
}
uint8_t AM_extended() {
AM_extended();
Address_extended();
return BUS().read();
}
//
void abx();
uint8_t adc(uint8_t operand, uint8_t data);
uint8_t add(uint8_t operand, uint8_t data, int carry = 0);
uint8_t neg(uint8_t operand);
register16_t m_d;

22
MC6809/src/mc6809.cpp
View File

@ -33,6 +33,16 @@ int EightBit::mc6809::execute(uint8_t cell) {
// ABX
case 0x3a: addCycles(3); abx(); break; // ABX (inherent)
// ADC
case 0x89: addCycles(2); A() = adc(A(), AM_immediate()); break; // ADC (ADCA, immediate)
case 0x99: addCycles(4); A() = adc(A(), AM_direct()); break; // ADC (ADCA, direct)
case 0xA9: addCycles(4); A() = adc(A(), AM_indexed()); break; // ADC (ADCA, indexed)
case 0xB9: addCycles(4); A() = adc(A(), AM_extended()); break; // ADC (ADCA, extended)
case 0xC9: addCycles(2); B() = adc(B(), AM_immediate()); break; // ADC (ADCB, immediate)
case 0xD9: addCycles(4); B() = adc(B(), AM_direct()); break; // ADC (ADCB, direct)
case 0xE9: addCycles(4); B() = adc(B(), AM_indexed()); break; // ADC (ADCB, indexed)
case 0xF9: addCycles(4); B() = adc(B(), AM_extended()); break; // ADC (ADCB, extended)
// NEG
case 0x00: addCycles(6); BUS().write(neg(AM_direct())); break; // NEG (direct)
case 0x40: addCycles(2); A() = neg(A()); break; // NEG (NEGA, inherent)
@ -62,4 +72,16 @@ uint8_t EightBit::mc6809::neg(uint8_t operand) {
setFlag(CC(), ZF, operand == 0);
setFlag(CC(), CF, result.word & Bit8);
return operand;
}
uint8_t EightBit::mc6809::adc(uint8_t operand, uint8_t data) {
return add(operand, data, CC() & CF);
}
uint8_t EightBit::mc6809::add(uint8_t operand, uint8_t data, int carry) {
const register16_t result = operand + data + carry;
setFlag(CC(), NF, result.low & Bit7);
setFlag(CC(), ZF, result.low == 0);
setFlag(CC(), CF, result.word & Bit8);
return result.low;
}