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Introduce the concept of a 'skip range' and spot one type of loader.

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This commit is contained in:
Thomas Harte
2025-12-03 17:46:12 -05:00
parent 90da2f2dcb
commit f11e2319eb
2 changed files with 58 additions and 14 deletions
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45
Machines/Commodore/Plus4/Plus4.cpp
View File

@@ -238,30 +238,33 @@ public:
audio_queue_.lock_flush();
}
// HACK. NOCOMMIT.
// int pulse_num_ = 0;
template <CPU::MOS6502Mk2::BusOperation operation, typename AddressT>
Cycles perform(const AddressT address, CPU::MOS6502Mk2::data_t<operation> value) {
// Determine from the TED video subsystem the length of this clock cycle as perceived by the 6502,
// relative to the master clock.
const auto length = video_.cycle_length(operation == CPU::MOS6502Mk2::BusOperation::Ready);
auto length = video_.cycle_length(operation == CPU::MOS6502Mk2::BusOperation::Ready);
// Update other subsystems.
timers_subcycles_ += length;
const auto timers_cycles = timers_subcycles_.divide(video_.timer_cycle_length());
timers_.tick(timers_cycles.as<int>());
advance_timers_and_tape(length);
if(operation != CPU::MOS6502Mk2::BusOperation::Ready && skip_range_) {
if(
operation == CPU::MOS6502Mk2::BusOperation::ReadOpcode &&
(address < skip_range_->low || address >= skip_range_->high)
) {
skip_range_ = std::nullopt;
}
length = Cycles(0);
} else {
video_.run_for(length);
tape_handler_.run_for(length);
video_.run_for(length);
if(c1541_) {
c1541_cycles_ += length * Cycles(1'000'000);
c1541_->run_for(c1541_cycles_.divide(media_divider_));
}
if(c1541_) {
c1541_cycles_ += length * Cycles(1'000'000);
c1541_->run_for(c1541_cycles_.divide(media_divider_));
time_since_audio_update_ += length;
}
time_since_audio_update_ += length;
if(operation == CPU::MOS6502Mk2::BusOperation::Ready) {
return length;
}
@@ -284,6 +287,12 @@ public:
value = io_direction_;
} else {
value = io_input();
if(!skip_range_) {
if(const auto pc = m6502_.registers().pc; pc >= 0x333 && pc < 0x3f2 ) {
skip_range_ = tape_handler_.skip_range(pc.full, m6502_, map_);
}
}
}
} else {
if(!address) {
@@ -676,7 +685,15 @@ private:
Serial::Bus serial_bus_;
SerialPort serial_port_;
void advance_timers_and_tape(const Cycles length) {
timers_subcycles_ += length;
const auto timers_cycles = timers_subcycles_.divide(video_.timer_cycle_length());
timers_.tick(timers_cycles.as<int>());
tape_handler_.run_for(length);
}
TapeHandler tape_handler_;
std::optional<SkipRange> skip_range_;
uint8_t io_direction_ = 0x00, io_output_ = 0x00;
uint8_t io_input() const {

27
Machines/Commodore/Plus4/TapeHandler.hpp
View File

@@ -13,9 +13,14 @@
#include "Storage/Tape/Parsers/Commodore.hpp"
#include <memory>
#include <optional>
namespace Commodore::Plus4 {
struct SkipRange {
uint16_t low, high;
};
/*!
All tape assistance, bundled into a single place, including:
@@ -181,6 +186,28 @@ struct TapeHandler: public ClockingHint::Observer {
return false;
}
template <typename M6502T, typename MemoryT>
std::optional<SkipRange> skip_range(const uint16_t pc, M6502T &, MemoryT &map) {
// Check for sequence:
//
// 24 01 BIT 01
// d0 fc BNE 3c8 <- PC will be here; trigger is the BIT operation above.
// 24 01 BIT 01
// f0 fc BEQ 3cc
if(
map.read(pc) == 0xd0 && map.read(pc+1) == 0xfc &&
map.read(pc-2) == 0x24 && map.read(pc-1) == 0x01 &&
map.read(pc+2) == 0x24 && map.read(pc+3) == 0x01 &&
map.read(pc+4) == 0xf0 && map.read(pc+5) == 0xfc
) {
return SkipRange{uint16_t(pc - 2), uint16_t(pc + 6)};
}
return std::nullopt;
}
private:
std::unique_ptr<Storage::Tape::BinaryTapePlayer> tape_player_;
bool play_button_ = false;