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Makes some effort at getting into interrupt processing.

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This commit is contained in:
Thomas Harte 2019-05-01 15:26:36 -04:00
parent f6ac407e4d
commit 2e5c0811e7
2 changed files with 69 additions and 48 deletions
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111
Processors/68000/Implementation/68000Implementation.hpp
View File

@ -54,6 +54,51 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
*/
switch(execution_state_) {
default:
case ExecutionState::Executing:
// Check for entry into the halted state.
if(halt_ && active_step_[0].microcycle.operation & Microcycle::NewAddress) {
execution_state_ = ExecutionState::Halted;
continue;
}
if(active_step_->microcycle.data_select_active()) {
// TODO: if valid peripheral address is asserted, substitute a
// synhronous bus access.
// Check whether the processor needs to await DTack.
if(!dtack_is_implicit && !dtack_ && !bus_error_) {
execution_state_ = ExecutionState::WaitingForDTack;
dtack_cycle_ = active_step_->microcycle;
dtack_cycle_.length = HalfCycles(2);
dtack_cycle_.operation &= ~(Microcycle::SelectByte | Microcycle::SelectWord);
continue;
}
// Check for bus error.
if(bus_error_ && !is_starting_interrupt_) {
active_program_ = nullptr;
active_micro_op_ = long_exception_micro_ops_;
active_step_ = active_micro_op_->bus_program;
populate_bus_error_steps(2, get_status(), get_bus_code(), *active_step_->microcycle.address);
}
}
// Check for an address error. Which I have assumed happens before the microcycle that
// would nominate the new address.
if(
(active_step_[0].microcycle.operation & Microcycle::NewAddress) &&
(active_step_[1].microcycle.operation & Microcycle::SelectWord) &&
*active_step_->microcycle.address & 1) {
active_program_ = nullptr;
active_micro_op_ = long_exception_micro_ops_;
active_step_ = active_micro_op_->bus_program;
populate_bus_error_steps(3, get_status(), get_bus_code(), *active_step_->microcycle.address);
}
// Perform the microcycle.
cycles_run_for +=
active_step_->microcycle.length +
bus_handler_.perform_bus_operation(active_step_->microcycle, is_supervisor_);
break;
case ExecutionState::Stopped:
@ -61,8 +106,8 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
// exit the STOP.
if(bus_interrupt_level_ > interrupt_level_) {
// TODO: schedule interrupt right here.
execution_state_ = ExecutionState::Executing;
break;
execution_state_ = ExecutionState::BeginInterrupt;
continue;
}
// Otherwise continue being stopped.
@ -75,7 +120,7 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
// If DTack or bus error has been signalled, stop waiting.
if(dtack_ || bus_error_) {
execution_state_ = ExecutionState::Executing;
break;
continue;
}
// Otherwise, signal another cycle of wait.
@ -85,58 +130,24 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
continue;
case ExecutionState::Halted:
if(!halt_) break;
if(!halt_) {
execution_state_ = ExecutionState::Executing;
continue;
}
cycles_run_for +=
stop_cycle_.length +
bus_handler_.perform_bus_operation(stop_cycle_, is_supervisor_);
continue;
}
// Check for entry into the halted state.
if(halt_ && active_step_[0].microcycle.operation & Microcycle::NewAddress) {
execution_state_ = ExecutionState::Halted;
continue;
}
if(active_step_->microcycle.data_select_active()) {
// TODO: if valid peripheral address is asserted, substitute a
// synhronous bus access.
// Check whether the processor needs to await DTack.
if(!dtack_is_implicit && !dtack_ && !bus_error_) {
execution_state_ = ExecutionState::WaitingForDTack;
dtack_cycle_ = active_step_->microcycle;
dtack_cycle_.length = HalfCycles(2);
dtack_cycle_.operation &= ~(Microcycle::SelectByte | Microcycle::SelectWord);
continue;
}
// Check for bus error.
if(bus_error_) {
case ExecutionState::BeginInterrupt:
active_program_ = nullptr;
active_micro_op_ = long_exception_micro_ops_;
active_step_ = active_micro_op_->bus_program;
populate_bus_error_steps(2, get_status(), get_bus_code(), *active_step_->microcycle.address);
}
active_micro_op_ = interrupt_micro_ops_;
execution_state_ = ExecutionState::Executing;
is_starting_interrupt_ = true;
break;
}
// Check for an address error. Which I have assumed happens before the microcycle that
// would nominate the new address.
if(
(active_step_[0].microcycle.operation & Microcycle::NewAddress) &&
(active_step_[1].microcycle.operation & Microcycle::SelectWord) &&
*active_step_->microcycle.address & 1) {
active_program_ = nullptr;
active_micro_op_ = long_exception_micro_ops_;
active_step_ = active_micro_op_->bus_program;
populate_bus_error_steps(3, get_status(), get_bus_code(), *active_step_->microcycle.address);
}
// Perform the microcycle.
cycles_run_for +=
active_step_->microcycle.length +
bus_handler_.perform_bus_operation(active_step_->microcycle, is_supervisor_);
#ifdef LOG_TRACE
if(!(active_step_->microcycle.operation & Microcycle::IsProgram)) {
@ -195,7 +206,10 @@ 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.
// TODO: is an interrupt pending?
if(bus_interrupt_level_ > interrupt_level_) {
execution_state_ = ExecutionState::BeginInterrupt;
break;
}
if(trace_flag_) {
// The user has set the trace bit in the status register.
@ -1805,6 +1819,9 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
// Otherwise, the vector is whatever we were just told it is.
effective_address_[0].full = source_bus_data_[0].halves.low.halves.low << 4;
// Let bus error go back to causing exceptions.
is_starting_interrupt_ = false;
break;
case int(MicroOp::Action::CopyNextWord):

6
Processors/68000/Implementation/68000Storage.hpp
View File

@ -35,7 +35,10 @@ class ProcessorStorage {
/// Occurs at the end of the current bus cycle after detection of the HALT input, continuing until
/// HALT is no longer signalled.
Halted
Halted,
/// Signals a transition from some other straight directly to cueing up an interrupt.
BeginInterrupt,
} execution_state_ = ExecutionState::Executing;
Microcycle dtack_cycle_;
Microcycle stop_cycle_;
@ -60,6 +63,7 @@ class ProcessorStorage {
bool halt_ = false;
int accepted_interrupt_level_ = 0;
bool is_starting_interrupt_ = false;
// Generic sources and targets for memory operations;
// by convention: [0] = source, [1] = destination.