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123 lines
3.6 KiB
C++
123 lines
3.6 KiB
C++
//
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// Nick.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 14/06/2021.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#pragma once
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#include <cstdint>
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#include "../../ClockReceiver/ClockReceiver.hpp"
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#include "../../Outputs/CRT/CRT.hpp"
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namespace Enterprise {
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class Nick {
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public:
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Nick(const uint8_t *ram);
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/// Writes to a Nick register; only the low two bits are decoded.
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void write(uint16_t address, uint8_t value);
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/// Reads from the Nick range. Nobody seems to be completely clear what
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/// this should return; I've set it up to return the last fetched video or mode
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/// line byte during periods when those things are being fetched, 0xff at all
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/// other times. Including during refresh, since I don't know what addresses
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/// are generated then.
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///
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/// This likely isn't accurate, but is the most accurate guess I could make.
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uint8_t read();
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void run_for(Cycles);
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Cycles get_time_until_z80_slot(Cycles after_period) const;
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void set_scan_target(Outputs::Display::ScanTarget *scan_target);
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Outputs::Display::ScanStatus get_scaled_scan_status() const;
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/// @returns The amount of time until the next potential change in interrupt output.
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Cycles next_sequence_point() const;
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/*!
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@returns The current state of the interrupt line — @c true for active;
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@c false for inactive.
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*/
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inline bool get_interrupt_line() const {
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return interrupt_line_;
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}
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/// Sets the type of output.
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void set_display_type(Outputs::Display::DisplayType);
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/// Gets the type of output.
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Outputs::Display::DisplayType get_display_type() const;
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private:
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Outputs::CRT::CRT crt_;
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const uint8_t *const ram_;
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// CPU-provided state.
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uint8_t line_parameter_control_ = 0xc0;
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uint16_t line_parameter_base_ = 0x0000;
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uint16_t border_colour_ = 0;
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// Ephemerals, related to current video position.
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int horizontal_counter_ = 0;
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uint16_t line_parameter_pointer_ = 0x0000;
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bool should_reload_line_parameters_ = true;
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uint16_t line_data_pointer_[2];
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uint16_t start_line_data_pointer_[2];
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mutable uint8_t last_read_ = 0xff;
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// Current mode line parameters.
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uint8_t lines_remaining_ = 0x00;
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uint8_t two_colour_mask_ = 0xff;
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int left_margin_ = 0, right_margin_ = 0;
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const uint16_t *alt_ind_palettes[4] = {palette_, palette_, palette_, palette_};
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enum class Mode {
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Vsync,
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Pixel,
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Attr,
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CH256,
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CH128,
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CH64,
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Unused,
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LPixel,
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} mode_ = Mode::Vsync;
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bool is_sync_or_pixels_ = false;
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int bpp_ = 0;
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int column_size_ = 0;
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bool interrupt_line_ = true;
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int line_data_per_column_increments_[2] = {0, 0};
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bool vres_ = false;
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bool reload_line_parameter_pointer_ = false;
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// The destination for new pixels.
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static constexpr int allocation_size = 336;
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static_assert((allocation_size % 16) == 0, "Allocation size must be a multiple of 16");
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uint16_t *pixel_pointer_ = nullptr, *allocated_pointer_ = nullptr;
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// Output transitions.
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enum class OutputType {
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Sync, Blank, Pixels, Border, ColourBurst
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};
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void set_output_type(OutputType, bool force_flush = false);
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int output_duration_ = 0;
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OutputType output_type_ = OutputType::Sync;
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// Current palette.
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uint16_t palette_[16]{};
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// The first column with pixels on it; will be either 8 or 10 depending
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// on whether the colour burst is meaningful to the current display type.
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int first_pixel_window_ = 10;
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// Specific outputters.
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template <int bpp, bool is_lpixel> void output_pixel(uint16_t *target, int columns) const;
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template <int bpp, int index_bits> void output_character(uint16_t *target, int columns) const;
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template <int bpp> void output_attributed(uint16_t *target, int columns) const;
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};
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}
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