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Add LSR implementation to the 6809 processor

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Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2018-08-21 21:59:25 +01:00
parent 05ca4166c7
commit c571956377
2 changed files with 21 additions and 11 deletions
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1
MC6809/inc/mc6809.h
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@ -213,6 +213,7 @@ namespace EightBit {
uint8_t inc(uint8_t operand);
uint8_t ld(uint8_t data);
register16_t ld(register16_t data);
uint8_t lsr(uint8_t operand);
uint8_t neg(uint8_t operand);
register16_t m_d;

31
MC6809/src/mc6809.cpp
View File

@ -91,7 +91,7 @@ int EightBit::mc6809::executeUnprefixed(uint8_t opcode) {
case 0x1c: addCycles(3); CC() = andr(CC(), AM_immediate_byte()); break; // AND (ANDCC, immediate)
// ASL
// ASL/LSL
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)
@ -242,6 +242,13 @@ int EightBit::mc6809::executeUnprefixed(uint8_t opcode) {
case 0x32: addCycles(4); S() = Address_indexed(); break; // LEA (LEAS indexed)
case 0x33: addCycles(4); U() = Address_indexed(); break; // LEA (LEAU indexed)
// LSR
case 0x04: addCycles(6); BUS().write(lsr(AM_direct_byte())); break; // LSR (LSR direct)
case 0x44: addCycles(2); A() = lsr(A()); break; // LSR (LSRA inherent)
case 0x54: addCycles(2); B() = lsr(B()); break; // LSR (LSRB inherent)
case 0x64: addCycles(6); BUS().write(lsr(AM_indexed_byte())); break; // LSR (LSR indexed)
case 0x74: addCycles(7); BUS().write(lsr(AM_extended_byte())); break; // LSR (LSR extended)
default:
UNREACHABLE;
}
@ -502,16 +509,14 @@ EightBit::register16_t EightBit::mc6809::add(register16_t operand, register16_t
}
uint8_t EightBit::mc6809::andr(uint8_t operand, uint8_t data) {
const uint8_t result = operand & data;
clearFlag(CC(), VF);
adjustNZ(result);
return result;
adjustNZ(operand &= data);
return operand;
}
uint8_t EightBit::mc6809::asl(uint8_t operand) {
setFlag(CC(), CF, operand & Bit7);
operand <<= 1;
adjustNZ(operand);
adjustNZ(operand <<= 1);
const auto overflow = (CC() & CF) ^ ((CC() & NF) >> 3);
setFlag(CC(), VF, overflow);
return operand;
@ -519,8 +524,7 @@ uint8_t EightBit::mc6809::asl(uint8_t operand) {
uint8_t EightBit::mc6809::asr(uint8_t operand) {
setFlag(CC(), CF, operand & Bit7);
operand >>= 1;
adjustNZ(operand);
adjustNZ(operand >>= 1);
return operand;
}
@ -585,10 +589,9 @@ uint8_t EightBit::mc6809::dec(uint8_t operand) {
}
uint8_t EightBit::mc6809::eor(uint8_t operand, uint8_t data) {
const uint8_t result = operand ^ data;
adjustNZ(result);
clearFlag(CC(), VF);
return result;
adjustNZ(operand ^= data);
return operand;
}
uint8_t& EightBit::mc6809::referenceTransfer8(int specifier) {
@ -657,3 +660,9 @@ EightBit::register16_t EightBit::mc6809::ld(register16_t data) {
adjustNZ(data);
return data;
}
uint8_t EightBit::mc6809::lsr(uint8_t operand) {
setFlag(CC(), CF, operand & Bit0);
adjustNZ(operand >>= 1);
return operand;
}