mirror of
https://github.com/TomHarte/CLK.git
synced 2024-11-29 12:50:28 +00:00
92 lines
2.2 KiB
C++
92 lines
2.2 KiB
C++
//
|
|
// Copper.cpp
|
|
// Clock Signal
|
|
//
|
|
// Created by Thomas Harte on 16/09/2021.
|
|
// Copyright © 2021 Thomas Harte. All rights reserved.
|
|
//
|
|
|
|
#include <stdio.h>
|
|
|
|
#define NDEBUG
|
|
#define LOG_PREFIX "[Copper] "
|
|
#include "../../Outputs/Log.hpp"
|
|
|
|
#include "Chipset.hpp"
|
|
#include "Copper.hpp"
|
|
|
|
using namespace Amiga;
|
|
|
|
bool Copper::advance(uint16_t position) {
|
|
switch(state_) {
|
|
default: return false;
|
|
|
|
case State::Waiting:
|
|
// TODO: blitter-finished bit.
|
|
if((position & position_mask_) >= instruction_[0]) {
|
|
state_ = State::FetchFirstWord;
|
|
}
|
|
return false;
|
|
|
|
case State::FetchFirstWord:
|
|
instruction_[0] = ram_[address_ & ram_mask_];
|
|
++address_;
|
|
state_ = State::FetchSecondWord;
|
|
break;
|
|
|
|
case State::FetchSecondWord: {
|
|
const bool should_skip_move = skip_next_;
|
|
skip_next_ = false;
|
|
|
|
instruction_[1] = ram_[address_ & ram_mask_];
|
|
++address_;
|
|
|
|
if(!(instruction_[0] & 1)) {
|
|
// A MOVE.
|
|
|
|
if(!should_skip_move) {
|
|
// Stop if this move would be a privilege violation.
|
|
instruction_[0] &= 0x1fe;
|
|
if((instruction_[0] < 0x10) || (instruction_[0] < 0x20 && !(control_&1))) {
|
|
LOG("Invalid MOVE to " << PADHEX(4) << instruction_[0] << "; stopping");
|
|
state_ = State::Stopped;
|
|
break;
|
|
}
|
|
|
|
// Construct a 68000-esque Microcycle in order to be able to perform the access.
|
|
CPU::MC68000::Microcycle cycle;
|
|
cycle.operation = CPU::MC68000::Microcycle::SelectWord;
|
|
uint32_t full_address = instruction_[0];
|
|
CPU::RegisterPair16 data = instruction_[1];
|
|
cycle.address = &full_address;
|
|
cycle.value = &data;
|
|
chipset_.perform(cycle);
|
|
}
|
|
|
|
// Roll onto the next command.
|
|
state_ = State::FetchFirstWord;
|
|
break;
|
|
}
|
|
|
|
// Prepare for a position comparison.
|
|
position_mask_ = 0x8001 | (instruction_[1] & 0x7ffe);
|
|
instruction_[0] &= position_mask_;
|
|
|
|
if(!(instruction_[1] & 1)) {
|
|
// A WAIT. Just note that this is now waiting; the proper test
|
|
// will be applied from the next potential `advance` onwards.
|
|
state_ = State::Waiting;
|
|
break;
|
|
}
|
|
|
|
// Neither a WAIT nor a MOVE => a SKIP.
|
|
|
|
// TODO: blitter-finished bit.
|
|
skip_next_ = (position & position_mask_) >= instruction_[0];
|
|
state_ = State::FetchFirstWord;
|
|
} break;
|
|
}
|
|
|
|
return true;
|
|
}
|