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Moves timing of interrupt sampling into prefetch queue advancement.

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As per comment, that is definitely the only place it can occur; I don't know whether it always occurs there.
This commit is contained in:
Thomas Harte 2019-08-04 21:06:34 -04:00
parent c6cf0e914b
commit 6a80832140
2 changed files with 15 additions and 2 deletions
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12
Processors/68000/Implementation/68000Implementation.hpp
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@ -188,6 +188,12 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
case BusStep::Action::AdvancePrefetch:
prefetch_queue_.halves.high = prefetch_queue_.halves.low;
// During prefetch advance seems to be the only time the interrupt inputs are sampled;
// TODO: determine whether this really happens on *every* advance.
if(bus_interrupt_level_ > interrupt_level_) {
pending_interrupt_level_ = bus_interrupt_level_;
}
break;
}
@ -199,6 +205,7 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
// If an interrupt (TODO: or reset) has finally arrived that will be serviced,
// exit the STOP.
if(bus_interrupt_level_ > interrupt_level_) {
pending_interrupt_level_ = bus_interrupt_level_;
execution_state_ = ExecutionState::BeginInterrupt;
continue;
}
@ -254,7 +261,7 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
// Either the micro-operations for this instruction have been exhausted, or
// no instruction was ongoing. Either way, do a standard instruction operation.
if(bus_interrupt_level_ > interrupt_level_) {
if(pending_interrupt_level_) {
execution_state_ = ExecutionState::BeginInterrupt;
break;
}
@ -1963,7 +1970,8 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
// a real 68000 uses the lower data strobe to collect the corresponding vector byte.
//
// Cf. M68000 8-/16-/32-BIT MICROPROCESSORS USER'S MANUAL 5.1.4.
accepted_interrupt_level_ = interrupt_level_ = bus_interrupt_level_;
accepted_interrupt_level_ = interrupt_level_ = pending_interrupt_level_;
pending_interrupt_level_ = 0;
effective_address_[0].full = 0xfffffff1 | uint32_t(accepted_interrupt_level_ << 1);
// Recede the program counter to where it would have been were there no

5
Processors/68000/Implementation/68000Storage.hpp
View File

@ -62,6 +62,11 @@ class ProcessorStorage {
bool bus_acknowledge_ = false;
bool halt_ = false;
// Holds the interrupt level that should be serviced at the next instruction
// dispatch, if any.
int pending_interrupt_level_ = 0;
// Holds the interrupt level that is currently being serviced.
// TODO: surely this doesn't need to be distinct from the pending_interrupt_level_?
int accepted_interrupt_level_ = 0;
bool is_starting_interrupt_ = false;