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118 lines
3.2 KiB
C++
118 lines
3.2 KiB
C++
//
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// Microdisc.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 22/11/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#include "Microdisc.hpp"
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using namespace Oric;
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namespace {
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// The number below, in cycles against an 8Mhz clock, was arrived at fairly unscientifically,
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// by comparing the amount of time this emulator took to show a directory versus a video of
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// a real Oric. It therefore assumes all other timing measurements were correct on the day
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// of the test. More work to do, I think.
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const int head_load_request_counter_target = 7653333;
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}
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Microdisc::Microdisc() :
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irq_enable_(false),
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delegate_(nullptr),
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paging_flags_(BASICDisable),
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head_load_request_counter_(-1),
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WD1770(P1793),
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last_control_(0) {
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set_control_register(last_control_, 0xff);
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}
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void Microdisc::set_disk(std::shared_ptr<Storage::Disk::Disk> disk, int drive) {
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if(!drives_[drive]) {
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drives_[drive].reset(new Storage::Disk::Drive);
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if(drive == selected_drive_) set_drive(drives_[drive]);
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}
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drives_[drive]->set_disk(disk);
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}
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void Microdisc::set_control_register(uint8_t control) {
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uint8_t changes = last_control_ ^ control;
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last_control_ = control;
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set_control_register(control, changes);
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}
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void Microdisc::set_control_register(uint8_t control, uint8_t changes) {
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// b2: data separator clock rate select (1 = double) [TODO]
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// b65: drive select
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if((changes >> 5)&3) {
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selected_drive_ = (control >> 5)&3;
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set_drive(drives_[selected_drive_]);
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}
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// b4: side select
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if(changes & 0x10) {
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unsigned int head = (control & 0x10) ? 1 : 0;
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for(int c = 0; c < 4; c++) {
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if(drives_[c]) drives_[c]->set_head(head);
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}
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}
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// b3: double density select (0 = double)
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if(changes & 0x08) {
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set_is_double_density(!(control & 0x08));
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}
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// b0: IRQ enable
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if(changes & 0x01) {
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bool had_irq = get_interrupt_request_line();
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irq_enable_ = !!(control & 0x01);
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bool has_irq = get_interrupt_request_line();
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if(has_irq != had_irq && delegate_) {
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delegate_->wd1770_did_change_output(this);
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}
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}
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// b7: EPROM select (0 = select)
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// b1: ROM disable (0 = disable)
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if(changes & 0x82) {
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paging_flags_ = ((control & 0x02) ? 0 : BASICDisable) | ((control & 0x80) ? MicrodscDisable : 0);
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if(delegate_) delegate_->microdisc_did_change_paging_flags(this);
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}
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}
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bool Microdisc::get_interrupt_request_line() {
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return irq_enable_ && WD1770::get_interrupt_request_line();
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}
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uint8_t Microdisc::get_interrupt_request_register() {
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return 0x7f | (WD1770::get_interrupt_request_line() ? 0x00 : 0x80);
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}
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uint8_t Microdisc::get_data_request_register() {
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return 0x7f | (get_data_request_line() ? 0x00 : 0x80);
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}
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void Microdisc::set_head_load_request(bool head_load) {
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set_motor_on(head_load);
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if(head_load) {
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head_load_request_counter_ = 0;
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} else {
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head_load_request_counter_ = head_load_request_counter_target;
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set_head_loaded(head_load);
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}
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}
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void Microdisc::run_for(const Cycles cycles) {
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if(head_load_request_counter_ < head_load_request_counter_target) {
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head_load_request_counter_ += cycles.as_int();
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if(head_load_request_counter_ >= head_load_request_counter_target) set_head_loaded(true);
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}
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WD::WD1770::run_for(cycles);
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}
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bool Microdisc::get_drive_is_ready() {
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return true;
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}
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