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92 lines
2.2 KiB
C++
92 lines
2.2 KiB
C++
//
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// Copper.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 16/09/2021.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#include <stdio.h>
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#define NDEBUG
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#define LOG_PREFIX "[Copper] "
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#include "../../Outputs/Log.hpp"
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#include "Chipset.hpp"
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#include "Copper.hpp"
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using namespace Amiga;
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bool Copper::advance(uint16_t position) {
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switch(state_) {
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default: return false;
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case State::Waiting:
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// TODO: blitter-finished bit.
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if((position & position_mask_) >= instruction_[0]) {
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state_ = State::FetchFirstWord;
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}
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return false;
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case State::FetchFirstWord:
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instruction_[0] = ram_[address_ & ram_mask_];
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++address_;
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state_ = State::FetchSecondWord;
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break;
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case State::FetchSecondWord: {
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const bool should_skip_move = skip_next_;
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skip_next_ = false;
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instruction_[1] = ram_[address_ & ram_mask_];
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++address_;
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if(!(instruction_[0] & 1)) {
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// A MOVE.
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if(!should_skip_move) {
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// Stop if this move would be a privilege violation.
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instruction_[0] &= 0x1fe;
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if((instruction_[0] < 0x10) || (instruction_[0] < 0x20 && !(control_&1))) {
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LOG("Invalid MOVE to " << PADHEX(4) << instruction_[0] << "; stopping");
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state_ = State::Stopped;
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break;
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}
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// Construct a 68000-esque Microcycle in order to be able to perform the access.
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CPU::MC68000::Microcycle cycle;
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cycle.operation = CPU::MC68000::Microcycle::SelectWord;
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uint32_t full_address = instruction_[0];
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CPU::RegisterPair16 data = instruction_[1];
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cycle.address = &full_address;
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cycle.value = &data;
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chipset_.perform(cycle);
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}
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// Roll onto the next command.
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state_ = State::FetchFirstWord;
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break;
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}
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// Prepare for a position comparison.
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position_mask_ = 0x8001 | (instruction_[1] & 0x7ffe);
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instruction_[0] &= position_mask_;
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if(!(instruction_[1] & 1)) {
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// A WAIT. Just note that this is now waiting; the proper test
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// will be applied from the next potential `advance` onwards.
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state_ = State::Waiting;
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break;
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}
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// Neither a WAIT nor a MOVE => a SKIP.
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// TODO: blitter-finished bit.
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skip_next_ = (position & position_mask_) >= instruction_[0];
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state_ = State::FetchFirstWord;
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} break;
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}
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return true;
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}
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