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534 lines
17 KiB
C++
534 lines
17 KiB
C++
//
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// 6560.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 05/06/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#ifndef _560_hpp
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#define _560_hpp
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#include "../../ClockReceiver/ClockReceiver.hpp"
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#include "../../Concurrency/AsyncTaskQueue.hpp"
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#include "../../Outputs/CRT/CRT.hpp"
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#include "../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
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#include "../../Outputs/Speaker/Implementation/SampleSource.hpp"
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namespace MOS {
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namespace MOS6560 {
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// audio state
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class AudioGenerator: public ::Outputs::Speaker::SampleSource {
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public:
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AudioGenerator(Concurrency::DeferringAsyncTaskQueue &audio_queue);
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void set_volume(uint8_t volume);
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void set_control(int channel, uint8_t value);
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// For ::SampleSource.
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void get_samples(std::size_t number_of_samples, int16_t *target);
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void skip_samples(std::size_t number_of_samples);
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void set_sample_volume_range(std::int16_t range);
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private:
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Concurrency::DeferringAsyncTaskQueue &audio_queue_;
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unsigned int counters_[4] = {2, 1, 0, 0}; // create a slight phase offset for the three channels
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unsigned int shift_registers_[4] = {0, 0, 0, 0};
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uint8_t control_registers_[4] = {0, 0, 0, 0};
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int16_t volume_ = 0;
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int16_t range_multiplier_ = 1;
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};
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struct BusHandler {
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void perform_read(uint16_t address, uint8_t *pixel_data, uint8_t *colour_data) {
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*pixel_data = 0xff;
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*colour_data = 0xff;
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}
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};
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enum class OutputMode {
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PAL, NTSC
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};
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/*!
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The 6560 Video Interface Chip ('VIC') is a video and audio output chip; it therefore vends both a @c CRT and a @c Speaker.
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To run the VIC for a cycle, the caller should call @c get_address, make the requested bus access
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and call @c set_graphics_value with the result.
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@c set_register and @c get_register provide register access.
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*/
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template <class BusHandler> class MOS6560 {
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public:
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MOS6560(BusHandler &bus_handler) :
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bus_handler_(bus_handler),
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crt_(new Outputs::CRT::CRT(65*4, 4, Outputs::CRT::DisplayType::NTSC60, 2)),
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audio_generator_(audio_queue_),
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speaker_(audio_generator_)
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{
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crt_->set_svideo_sampling_function(
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"vec2 svideo_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase)"
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"{"
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"vec2 yc = texture(texID, coordinate).rg / vec2(255.0);"
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"float phaseOffset = 6.283185308 * 2.0 * yc.y;"
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"float chroma = step(yc.y, 0.75) * cos(phase + phaseOffset);"
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"return vec2(yc.x, chroma);"
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"}");
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// default to s-video output
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crt_->set_video_signal(Outputs::CRT::VideoSignal::SVideo);
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// default to NTSC
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set_output_mode(OutputMode::NTSC);
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}
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~MOS6560() {
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audio_queue_.flush();
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}
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void set_clock_rate(double clock_rate) {
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speaker_.set_input_rate(static_cast<float>(clock_rate / 4.0));
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}
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Outputs::CRT::CRT *get_crt() { return crt_.get(); }
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Outputs::Speaker::Speaker *get_speaker() { return &speaker_; }
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void set_high_frequency_cutoff(float cutoff) {
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speaker_.set_high_frequency_cutoff(cutoff);
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}
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/*!
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Sets the output mode to either PAL or NTSC.
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*/
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void set_output_mode(OutputMode output_mode) {
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output_mode_ = output_mode;
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// Luminances are encoded trivially: on a 0–255 scale.
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const uint8_t luminances[16] = {
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0, 255, 64, 192,
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128, 128, 64, 192,
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128, 192, 128, 255,
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192, 192, 128, 255
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};
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// Chrominances are encoded such that 0–128 is a complete revolution of phase;
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// anything above 191 disables the colour subcarrier. Phase is relative to the
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// colour burst, so 0 is green.
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const uint8_t pal_chrominances[16] = {
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255, 255, 37, 101,
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19, 86, 123, 59,
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46, 53, 37, 101,
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19, 86, 123, 59,
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};
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const uint8_t ntsc_chrominances[16] = {
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255, 255, 7, 71,
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25, 86, 48, 112,
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0, 119, 7, 71,
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25, 86, 48, 112,
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};
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const uint8_t *chrominances;
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Outputs::CRT::DisplayType display_type;
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switch(output_mode) {
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default:
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chrominances = pal_chrominances;
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display_type = Outputs::CRT::DisplayType::PAL50;
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timing_.cycles_per_line = 71;
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timing_.line_counter_increment_offset = 4;
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timing_.final_line_increment_position = timing_.cycles_per_line - timing_.line_counter_increment_offset;
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timing_.lines_per_progressive_field = 312;
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timing_.supports_interlacing = false;
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break;
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case OutputMode::NTSC:
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chrominances = ntsc_chrominances;
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display_type = Outputs::CRT::DisplayType::NTSC60;
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timing_.cycles_per_line = 65;
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timing_.line_counter_increment_offset = 40;
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timing_.final_line_increment_position = 58;
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timing_.lines_per_progressive_field = 261;
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timing_.supports_interlacing = true;
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break;
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}
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crt_->set_new_display_type(static_cast<unsigned int>(timing_.cycles_per_line*4), display_type);
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switch(output_mode) {
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case OutputMode::PAL:
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crt_->set_visible_area(Outputs::CRT::Rect(0.1f, 0.07f, 0.9f, 0.9f));
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break;
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case OutputMode::NTSC:
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crt_->set_visible_area(Outputs::CRT::Rect(0.05f, 0.05f, 0.9f, 0.9f));
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break;
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}
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for(int c = 0; c < 16; c++) {
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uint8_t *colour = reinterpret_cast<uint8_t *>(&colours_[c]);
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colour[0] = luminances[c];
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colour[1] = chrominances[c];
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}
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}
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/*!
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Runs for cycles. Derr.
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*/
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inline void run_for(const Cycles cycles) {
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// keep track of the amount of time since the speaker was updated; lazy updates are applied
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cycles_since_speaker_update_ += cycles;
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int number_of_cycles = cycles.as_int();
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while(number_of_cycles--) {
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// keep an old copy of the vertical count because that test is a cycle later than the actual changes
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int previous_vertical_counter = vertical_counter_;
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// keep track of internal time relative to this scanline
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horizontal_counter_++;
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if(horizontal_counter_ == timing_.cycles_per_line) {
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if(horizontal_drawing_latch_) {
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current_character_row_++;
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if(
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(current_character_row_ == 16) ||
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(current_character_row_ == 8 && !registers_.tall_characters)
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) {
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current_character_row_ = 0;
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current_row_++;
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}
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pixel_line_cycle_ = -1;
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columns_this_line_ = -1;
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column_counter_ = -1;
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}
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horizontal_counter_ = 0;
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if(output_mode_ == OutputMode::PAL) is_odd_line_ ^= true;
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horizontal_drawing_latch_ = false;
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vertical_counter_ ++;
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if(vertical_counter_ == lines_this_field()) {
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vertical_counter_ = 0;
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if(output_mode_ == OutputMode::NTSC) is_odd_frame_ ^= true;
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current_row_ = 0;
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rows_this_field_ = -1;
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vertical_drawing_latch_ = false;
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base_video_matrix_address_counter_ = 0;
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current_character_row_ = 0;
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}
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}
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// check for vertical starting events
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vertical_drawing_latch_ |= registers_.first_row_location == (previous_vertical_counter >> 1);
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horizontal_drawing_latch_ |= vertical_drawing_latch_ && (horizontal_counter_ == registers_.first_column_location);
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if(pixel_line_cycle_ >= 0) pixel_line_cycle_++;
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switch(pixel_line_cycle_) {
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case -1:
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if(horizontal_drawing_latch_) {
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pixel_line_cycle_ = 0;
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video_matrix_address_counter_ = base_video_matrix_address_counter_;
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}
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break;
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case 1: columns_this_line_ = registers_.number_of_columns; break;
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case 2: if(rows_this_field_ < 0) rows_this_field_ = registers_.number_of_rows; break;
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case 3: if(current_row_ < rows_this_field_) column_counter_ = 0; break;
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}
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uint16_t fetch_address = 0x1c;
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if(column_counter_ >= 0 && column_counter_ < columns_this_line_*2) {
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if(column_counter_&1) {
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fetch_address = registers_.character_cell_start_address + (character_code_*(registers_.tall_characters ? 16 : 8)) + current_character_row_;
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} else {
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fetch_address = static_cast<uint16_t>(registers_.video_matrix_start_address + video_matrix_address_counter_);
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video_matrix_address_counter_++;
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if(
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(current_character_row_ == 15) ||
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(current_character_row_ == 7 && !registers_.tall_characters)
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) {
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base_video_matrix_address_counter_ = video_matrix_address_counter_;
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}
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}
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}
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fetch_address &= 0x3fff;
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uint8_t pixel_data;
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uint8_t colour_data;
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bus_handler_.perform_read(fetch_address, &pixel_data, &colour_data);
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// TODO: there should be a further two-cycle delay on pixels being output; the reverse bit should
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// divide the byte it is set for 3:1 and then continue as usual.
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// determine output state; colour burst and sync timing are currently a guess
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if(horizontal_counter_ > timing_.cycles_per_line-4) this_state_ = State::ColourBurst;
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else if(horizontal_counter_ > timing_.cycles_per_line-7) this_state_ = State::Sync;
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else {
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this_state_ = (column_counter_ >= 0 && column_counter_ < columns_this_line_*2) ? State::Pixels : State::Border;
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}
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// apply vertical sync
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if(
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(vertical_counter_ < 3 && is_odd_frame()) ||
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(registers_.interlaced &&
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(
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(vertical_counter_ == 0 && horizontal_counter_ > 32) ||
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(vertical_counter_ == 1) || (vertical_counter_ == 2) ||
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(vertical_counter_ == 3 && horizontal_counter_ <= 32)
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)
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))
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this_state_ = State::Sync;
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// update the CRT
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if(this_state_ != output_state_) {
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switch(output_state_) {
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case State::Sync: crt_->output_sync(cycles_in_state_ * 4); break;
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case State::ColourBurst: crt_->output_colour_burst(cycles_in_state_ * 4, (is_odd_frame_ || is_odd_line_) ? 128 : 0); break;
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case State::Border: output_border(cycles_in_state_ * 4); break;
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case State::Pixels: crt_->output_data(cycles_in_state_ * 4); break;
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}
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output_state_ = this_state_;
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cycles_in_state_ = 0;
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pixel_pointer = nullptr;
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if(output_state_ == State::Pixels) {
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pixel_pointer = reinterpret_cast<uint16_t *>(crt_->allocate_write_area(260));
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}
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}
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cycles_in_state_++;
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if(this_state_ == State::Pixels) {
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// TODO: palette changes can happen within half-characters; the below needs to be divided.
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// Also: a perfect opportunity to rearrange this inner loop for no longer needing to be
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// two parts with a cooperative owner?
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if(column_counter_&1) {
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character_value_ = pixel_data;
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if(pixel_pointer) {
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uint16_t cell_colour = colours_[character_colour_ & 0x7];
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if(!(character_colour_&0x8)) {
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uint16_t colours[2];
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if(registers_.invertedCells) {
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colours[0] = cell_colour;
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colours[1] = registers_.backgroundColour;
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} else {
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colours[0] = registers_.backgroundColour;
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colours[1] = cell_colour;
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}
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pixel_pointer[0] = colours[(character_value_ >> 7)&1];
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pixel_pointer[1] = colours[(character_value_ >> 6)&1];
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pixel_pointer[2] = colours[(character_value_ >> 5)&1];
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pixel_pointer[3] = colours[(character_value_ >> 4)&1];
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pixel_pointer[4] = colours[(character_value_ >> 3)&1];
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pixel_pointer[5] = colours[(character_value_ >> 2)&1];
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pixel_pointer[6] = colours[(character_value_ >> 1)&1];
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pixel_pointer[7] = colours[(character_value_ >> 0)&1];
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} else {
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uint16_t colours[4] = {registers_.backgroundColour, registers_.borderColour, cell_colour, registers_.auxiliary_colour};
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pixel_pointer[0] =
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pixel_pointer[1] = colours[(character_value_ >> 6)&3];
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pixel_pointer[2] =
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pixel_pointer[3] = colours[(character_value_ >> 4)&3];
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pixel_pointer[4] =
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pixel_pointer[5] = colours[(character_value_ >> 2)&3];
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pixel_pointer[6] =
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pixel_pointer[7] = colours[(character_value_ >> 0)&3];
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}
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pixel_pointer += 8;
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}
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} else {
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character_code_ = pixel_data;
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character_colour_ = colour_data;
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}
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}
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// Keep counting columns even if sync or the colour burst have interceded.
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if(column_counter_ >= 0 && column_counter_ < columns_this_line_*2) {
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column_counter_++;
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}
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}
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}
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/*!
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Causes the 6560 to flush as much pending CRT and speaker communications as possible.
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*/
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inline void flush() {
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update_audio();
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audio_queue_.perform();
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}
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/*!
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Writes to a 6560 register.
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*/
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void set_register(int address, uint8_t value) {
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address &= 0xf;
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registers_.direct_values[address] = value;
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switch(address) {
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case 0x0:
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registers_.interlaced = !!(value&0x80) && timing_.supports_interlacing;
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registers_.first_column_location = value & 0x7f;
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break;
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case 0x1:
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registers_.first_row_location = value;
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break;
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case 0x2:
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registers_.number_of_columns = value & 0x7f;
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registers_.video_matrix_start_address = static_cast<uint16_t>((registers_.video_matrix_start_address & 0x3c00) | ((value & 0x80) << 2));
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break;
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case 0x3:
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registers_.number_of_rows = (value >> 1)&0x3f;
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registers_.tall_characters = !!(value&0x01);
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break;
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case 0x5:
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registers_.character_cell_start_address = static_cast<uint16_t>((value & 0x0f) << 10);
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registers_.video_matrix_start_address = static_cast<uint16_t>((registers_.video_matrix_start_address & 0x0200) | ((value & 0xf0) << 6));
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break;
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case 0xa:
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case 0xb:
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case 0xc:
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case 0xd:
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update_audio();
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audio_generator_.set_control(address - 0xa, value);
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break;
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case 0xe:
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update_audio();
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registers_.auxiliary_colour = colours_[value >> 4];
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audio_generator_.set_volume(value & 0xf);
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break;
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case 0xf: {
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uint16_t new_border_colour = colours_[value & 0x07];
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if(this_state_ == State::Border && new_border_colour != registers_.borderColour) {
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output_border(cycles_in_state_ * 4);
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cycles_in_state_ = 0;
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}
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registers_.invertedCells = !((value >> 3)&1);
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registers_.borderColour = new_border_colour;
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registers_.backgroundColour = colours_[value >> 4];
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}
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break;
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// TODO: the lightpen, etc
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default:
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break;
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}
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}
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/*
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Reads from a 6560 register.
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*/
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uint8_t get_register(int address) {
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address &= 0xf;
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switch(address) {
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default: return registers_.direct_values[address];
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case 0x03: return static_cast<uint8_t>(raster_value() << 7) | (registers_.direct_values[3] & 0x7f);
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case 0x04: return (raster_value() >> 1) & 0xff;
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}
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}
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private:
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BusHandler &bus_handler_;
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std::unique_ptr<Outputs::CRT::CRT> crt_;
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Concurrency::DeferringAsyncTaskQueue audio_queue_;
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AudioGenerator audio_generator_;
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Outputs::Speaker::LowpassSpeaker<AudioGenerator> speaker_;
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Cycles cycles_since_speaker_update_;
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void update_audio() {
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speaker_.run_for(audio_queue_, Cycles(cycles_since_speaker_update_.divide(Cycles(4))));
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}
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// register state
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struct {
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bool interlaced, tall_characters;
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uint8_t first_column_location, first_row_location;
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uint8_t number_of_columns, number_of_rows;
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uint16_t character_cell_start_address, video_matrix_start_address;
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uint16_t backgroundColour, borderColour, auxiliary_colour;
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bool invertedCells;
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uint8_t direct_values[16];
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} registers_;
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// output state
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enum State {
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Sync, ColourBurst, Border, Pixels
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} this_state_, output_state_;
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unsigned int cycles_in_state_;
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// counters that cover an entire field
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int horizontal_counter_ = 0, vertical_counter_ = 0;
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const int lines_this_field() {
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// Necessary knowledge here: only the NTSC 6560 supports interlaced video.
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return registers_.interlaced ? (is_odd_frame_ ? 262 : 263) : timing_.lines_per_progressive_field;
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}
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const int raster_value() {
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const int bonus_line = (horizontal_counter_ + timing_.line_counter_increment_offset) / timing_.cycles_per_line;
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const int line = vertical_counter_ + bonus_line;
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const int final_line = lines_this_field();
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if(line < final_line)
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||
return line;
|
||
|
||
if(is_odd_frame()) {
|
||
return (horizontal_counter_ >= timing_.final_line_increment_position) ? 0 : final_line - 1;
|
||
} else {
|
||
return line % final_line;
|
||
}
|
||
// Cf. http://www.sleepingelephant.com/ipw-web/bulletin/bb/viewtopic.php?f=14&t=7237&start=15#p80737
|
||
}
|
||
bool is_odd_frame() {
|
||
return is_odd_frame_ || !registers_.interlaced;
|
||
}
|
||
|
||
// latches dictating start and length of drawing
|
||
bool vertical_drawing_latch_, horizontal_drawing_latch_;
|
||
int rows_this_field_, columns_this_line_;
|
||
|
||
// current drawing position counter
|
||
int pixel_line_cycle_, column_counter_;
|
||
int current_row_;
|
||
uint16_t current_character_row_;
|
||
uint16_t video_matrix_address_counter_, base_video_matrix_address_counter_;
|
||
|
||
// data latched from the bus
|
||
uint8_t character_code_, character_colour_, character_value_;
|
||
|
||
bool is_odd_frame_ = false, is_odd_line_ = false;
|
||
|
||
// lookup table from 6560 colour index to appropriate PAL/NTSC value
|
||
uint16_t colours_[16];
|
||
|
||
uint16_t *pixel_pointer;
|
||
void output_border(unsigned int number_of_cycles) {
|
||
uint16_t *colour_pointer = reinterpret_cast<uint16_t *>(crt_->allocate_write_area(1));
|
||
if(colour_pointer) *colour_pointer = registers_.borderColour;
|
||
crt_->output_level(number_of_cycles);
|
||
}
|
||
|
||
struct {
|
||
int cycles_per_line;
|
||
int line_counter_increment_offset;
|
||
int final_line_increment_position;
|
||
int lines_per_progressive_field;
|
||
bool supports_interlacing;
|
||
} timing_;
|
||
OutputMode output_mode_;
|
||
};
|
||
|
||
}
|
||
}
|
||
|
||
#endif /* _560_hpp */
|