6502/EightBit
1
0
Fork 0
mirror of https://github.com/MoleskiCoder/EightBit.git synced 2025-02-02 23:30:49 +00:00
Code Issues Projects Releases Wiki Activity

First stab at interrupt handling on the 6809 processor.

Browse Source 
Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2018-08-24 12:14:14 +01:00
parent 1eb59279a8
commit 21e8360dc1
2 changed files with 44 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
MC6809/inc/mc6809.h
View File

@ -122,6 +122,12 @@ namespace EightBit {
void execute10(uint8_t opcode);
void execute11(uint8_t opcode);
// Interrupt handlers
void handleNMI();
void handleIRQ();
void handleFIRQ();
// Register selection for "indexed"
register16_t& RR(int which);

40
MC6809/src/mc6809.cpp
View File

@ -13,19 +13,55 @@ int EightBit::mc6809::step() {
if (LIKELY(powered())) {
m_prefix10 = m_prefix11 = false;
ExecutingInstruction.fire(*this);
return execute(fetchByte());
if (lowered(NMI()))
handleNMI();
else if (lowered(FIRQ()) && !(CC() & FF))
handleFIRQ();
else if (lowered(IRQ()) && !(CC() & IF))
handleIRQ();
else
execute(fetchByte());
ExecutedInstruction.fire(*this);
}
return cycles();
}
// Interrupt (etc.) handlers
void EightBit::mc6809::reset() {
Processor::reset();
DP() = 0; // Reestablish zero page
CC() |= (IF & FF); // Disable interrupts
CC() |= (IF & FF); // Disable IRQ and FIRQ
jump(getWordPaged(0xff, RESETvector));
}
void EightBit::mc6809::handleNMI() {
raise(NMI());
addCycles(21);
saveEntireRegisterState();
jump(getWordPaged(0xff, NMIvector));
}
void EightBit::mc6809::handleIRQ() {
raise(IRQ());
addCycles(21);
saveEntireRegisterState();
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
pushWordS(PC());
pushS(CC());
CC() |= (IF & FF); // Disable IRQ and FIRQ
jump(getWordPaged(0xff, FIRQvector));
}
//
int EightBit::mc6809::execute(uint8_t opcode) {
const bool prefixed = m_prefix10 || m_prefix11;
if (LIKELY(!prefixed)) {