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Ensures the value initially loaded to A7 is aligned.

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This is a bit of a guess; it's likely to be true though per the rule that A7 is always kept aligned.
This commit is contained in:
Thomas Harte 2021-07-25 19:55:23 -04:00
parent fcd6b7b0ea
commit b7bed027d7
3 changed files with 19 additions and 1 deletions
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13
Processors/68000/Implementation/68000Implementation.hpp
View File

@ -191,6 +191,11 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
case BusStep::Action::DecrementEffectiveAddress1: effective_address_[1].full -= 2; break;
case BusStep::Action::IncrementProgramCounter: program_counter_.full += 2; break;
case BusStep::Action::IncrementEffectiveAddress0AlignStackPointer:
effective_address_[0].full += 2;
address_[7].full &= 0xffff'fffe;
break;
case BusStep::Action::AdvancePrefetch:
prefetch_queue_.halves.high = prefetch_queue_.halves.low;
@ -299,6 +304,14 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
}
#endif
static uint32_t last_a7 = address_[7].full;
log |= (program_counter_.full - 4 == 0x00fcafba);
// if(log) {
if(log && last_a7 != address_[7].full) {
last_a7 = address_[7].full;
printf("%08x a7:%08x\n", program_counter_.full - 4, address_[7].full);
}
decoded_instruction_.full = prefetch_queue_.halves.high.full;
#ifndef NDEBUG

2
Processors/68000/Implementation/68000Storage.cpp
View File

@ -261,7 +261,7 @@ struct ProcessorStorageConstructor {
steps.push_back(step);
step.microcycle.operation = Microcycle::SameAddress | Microcycle::Read | Microcycle::IsProgram | Microcycle::SelectWord;
step.action = Action::IncrementEffectiveAddress0;
step.action = isupper(access_pattern[1]) ? Action::IncrementEffectiveAddress0 : Action::IncrementEffectiveAddress0AlignStackPointer;
steps.push_back(step);
continue;

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

@ -196,6 +196,9 @@ class ProcessorStorage {
/// Copies prefetch_queue_[1] to prefetch_queue_[0].
AdvancePrefetch,
/// Performs effective_address_[0] += 2 and zeroes the final bit of the stack pointer.
IncrementEffectiveAddress0AlignStackPointer,
/*!
Terminates an atomic program; if nothing else is pending, schedules the next instruction.
This action is special in that it usurps any included microcycle. So any Step with this
@ -550,6 +553,8 @@ class ProcessorStorage {
inline uint16_t get_status() const;
inline void set_status(uint16_t);
bool log = false;
private:
friend struct ProcessorStorageConstructor;
friend class ProcessorStorageTests;