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Edge towards but don't quite reach interrupt.

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This commit is contained in:
Thomas Harte 2023-11-20 22:52:20 -05:00
parent 695282b838
commit c4e9f75709
1 changed files with 35 additions and 4 deletions
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39
Machines/PCCompatible/PCCompatible.cpp
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@ -87,10 +87,20 @@ class PIC {
template <int input>
void apply_edge(bool final_level) {
const uint8_t input_mask = 1 << input;
if(mask_ & input_mask) {
return;
// Guess: level triggered means the request can be forwarded only so long as the
// relevant input is actually high. Whereas edge triggered implies capturing state.
if(level_triggered_) {
requests_ &= ~input_mask;
}
printf("PIC: Unmasked input %d switches to level %d\n", input, final_level);
if(final_level) {
requests_ |= input_mask;
}
}
bool pending() {
// Per the OSDev Wiki, masking is applied after the fact.
return requests_ & ~mask_;
}
private:
@ -102,6 +112,9 @@ class PIC {
uint8_t vector_base_ = 0;
uint8_t mask_ = 0;
uint8_t requests_ = 0;
uint8_t in_service_ = 0;
struct ConfgurationState {
int word;
bool has_fourth_word;
@ -661,12 +674,29 @@ class ConcreteMachine:
void run_for(const Cycles cycles) override {
auto instructions = cycles.as_integral();
while(instructions--) {
//
// First draft: all hardware runs in lockstep.
//
// Advance the PIT.
pit_.run_for(PitDivisor / PitMultiplier);
// Get the next thing to execute into decoded.
// Query for interrupts and apply if pending.
if(pic_.pending() && context.flags.flag<InstructionSet::x86::Flag::Interrupt>()) {
// Regress the IP if a REP is in-progress so as to resume it later.
if(context.flow_controller.should_repeat()) {
context.registers.ip() = decoded_ip_;
context.flow_controller.begin_instruction();
}
// TODO: signal interrupt.
printf("TODO: should interrupt\n");
}
// Get the next thing to execute.
if(!context.flow_controller.should_repeat()) {
// Decode from the current IP.
decoded_ip_ = context.registers.ip();
const auto remainder = context.memory.next_code();
decoded = decoder.decode(remainder.first, remainder.second);
@ -735,6 +765,7 @@ class ConcreteMachine:
InstructionSet::x86::Decoder8086 decoder;
// InstructionSet::x86::Decoder<InstructionSet::x86::Model::i8086> decoder;
uint16_t decoded_ip_ = 0;
std::pair<int, InstructionSet::x86::Instruction<false>> decoded;
};