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Add ASL/ASR instructions 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 16:18:06 +01:00
parent a125c4c24c
commit d17cd1777a
2 changed files with 43 additions and 6 deletions
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10
MC6809/inc/mc6809.h
View File

@ -106,11 +106,21 @@ namespace EightBit {
register16_t AM_indexed_word();
register16_t AM_extended_word();
void adjustZero(uint8_t datum) { clearFlag(CC(), ZF, datum); }
void adjustNegative(uint8_t datum) { setFlag(CC(), NF, datum & NF); }
void adjustNZ(uint8_t datum) {
adjustZero(datum);
adjustNegative(datum);
}
void abx();
uint8_t adc(uint8_t operand, uint8_t data);
uint8_t add(uint8_t operand, uint8_t data, int 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);
uint8_t asr(uint8_t operand);
uint8_t neg(uint8_t operand);
register16_t m_d;

39
MC6809/src/mc6809.cpp
View File

@ -73,6 +73,20 @@ int EightBit::mc6809::execute(uint8_t cell) {
case 0x1c: addCycles(3); CC() = andr(CC(), AM_immediate_byte()); break; // AND (ANDCC, immediate)
// ASL
case 0x08: addCycles(6); BUS().write(asl(AM_direct_byte())); break; // ASL (ASL, direct)
case 0x48: addCycles(2); A() = asl(A()); break; // ASL (ASLA, inherent)
case 0x58: addCycles(2); B() = asl(B()); break; // ASL (ASLB, inherent)
case 0x68: addCycles(6); BUS().write(asl(AM_indexed_byte())); break; // ASL (ASL, indexed)
case 0x78: addCycles(7); BUS().write(asl(AM_extended_byte())); break; // ASL (ASL, extended)
// ASR
case 0x07: addCycles(6); BUS().write(asr(AM_direct_byte())); break; // ASR (ASR, direct)
case 0x47: addCycles(2); A() = asr(A()); break; // ASR (ASRA, inherent)
case 0x57: addCycles(2); B() = asr(B()); break; // ASR (ASRB, inherent)
case 0x67: addCycles(6); BUS().write(asr(AM_indexed_byte())); break; // ASR (ASR, indexed)
case 0x77: addCycles(7); BUS().write(asr(AM_extended_byte())); break; // ASR (ASR, extended)
// NEG
case 0x00: addCycles(6); BUS().write(neg(AM_direct_byte())); break; // NEG (direct)
case 0x40: addCycles(2); A() = neg(A()); break; // NEG (NEGA, inherent)
@ -239,8 +253,7 @@ uint8_t EightBit::mc6809::neg(uint8_t operand) {
setFlag(CC(), VF, operand == Bit7);
const register16_t result = 0 - operand;
operand = result.low;
setFlag(CC(), NF, operand & Bit7);
setFlag(CC(), ZF, operand == 0);
adjustNZ(operand);
setFlag(CC(), CF, result.word & Bit8);
return operand;
}
@ -251,8 +264,7 @@ uint8_t EightBit::mc6809::adc(uint8_t operand, uint8_t data) {
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);
adjustNZ(result.low);
setFlag(CC(), CF, result.word & Bit8);
return result.low;
}
@ -269,7 +281,22 @@ EightBit::register16_t EightBit::mc6809::add(register16_t operand, register16_t
uint8_t EightBit::mc6809::andr(uint8_t operand, uint8_t data) {
const auto result = operand & data;
clearFlag(CC(), VF);
setFlag(CC(), NF, result & Bit7);
setFlag(CC(), ZF, result == 0);
adjustNZ(result);
return result;
}
uint8_t EightBit::mc6809::asl(uint8_t operand) {
setFlag(CC(), CF, operand & Bit7);
operand <<= 1;
adjustNZ(operand);
const auto overflow = (CC() & CF) ^ ((CC() & NF) >> 3);
setFlag(CC(), overflow);
return operand;
}
uint8_t EightBit::mc6809::asr(uint8_t operand) {
setFlag(CC(), CF, operand & Bit7);
operand >>= 1;
adjustNZ(operand);
return operand;
}