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255 lines
6.9 KiB
C++
255 lines
6.9 KiB
C++
//
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// Video.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 04/10/2019.
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// Copyright © 2019 Thomas Harte. All rights reserved.
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//
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#ifndef Atari_ST_Video_hpp
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#define Atari_ST_Video_hpp
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#include "../../../Outputs/CRT/CRT.hpp"
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#include "../../../ClockReceiver/ClockReceiver.hpp"
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#include "../../../ClockReceiver/DeferredQueue.hpp"
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#include <vector>
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// Testing hook; not for any other user.
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class VideoTester;
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namespace Atari {
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namespace ST {
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struct LineLength {
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int length = 1024;
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int hsync_start = 1024;
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int hsync_end = 1024;
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};
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/*!
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Models a combination of the parts of the GLUE, MMU and Shifter that in net
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form the video subsystem of the Atari ST. So not accurate to a real chip, but
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(hopefully) to a subsystem.
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*/
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class Video {
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public:
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Video();
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/*!
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Sets the memory pool that provides video, and its size.
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*/
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void set_ram(uint16_t *, size_t size);
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/*!
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Sets the target device for video data.
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*/
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void set_scan_target(Outputs::Display::ScanTarget *scan_target);
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/// Gets the current scan status.
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Outputs::Display::ScanStatus get_scaled_scan_status() const;
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/*!
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Sets the type of output.
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*/
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void set_display_type(Outputs::Display::DisplayType);
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/*!
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Gets the type of output.
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*/
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Outputs::Display::DisplayType get_display_type() const;
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/*!
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Produces the next @c duration period of pixels.
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*/
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void run_for(HalfCycles duration);
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/*!
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@returns the number of cycles until there is next a change in the hsync,
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vsync or display_enable outputs.
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*/
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HalfCycles get_next_sequence_point();
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/*!
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@returns @c true if the horizontal sync output is currently active; @c false otherwise.
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@discussion On an Atari ST, this generates a VPA-style interrupt, which is often erroneously
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documented as being triggered by horizontal blank.
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*/
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bool hsync();
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/*!
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@returns @c true if the vertical sync output is currently active; @c false otherwise.
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@discussion On an Atari ST, this generates a VPA-style interrupt, which is often erroneously
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documented as being triggered by vertical blank.
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*/
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bool vsync();
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/*!
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@returns @c true if the display enabled output is currently active; @c false otherwise.
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@discussion On an Atari ST this is fed to the MFP. The documentation that I've been able to
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find implies a total 28-cycle delay between the real delay enabled signal changing and its effect
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on the 68000 interrupt input via the MFP. As I have yet to determine how much delay is caused
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by the MFP a full 28-cycle delay is applied by this class. This should be dialled down when the
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MFP's responsibility is clarified.
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*/
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bool display_enabled();
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/// @returns the effect of reading from @c address; only the low 6 bits are decoded.
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uint16_t read(int address);
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/// Writes @c value to @c address, of which only the low 6 bits are decoded.
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void write(int address, uint16_t value);
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/// Used internally to track state.
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enum class FieldFrequency {
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Fifty = 0, Sixty = 1, SeventyTwo = 2
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};
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struct RangeObserver {
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/// Indicates to the observer that the memory access range has changed.
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virtual void video_did_change_access_range(Video *) = 0;
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};
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/// Sets a range observer, which is an actor that will be notified if the memory access range changes.
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void set_range_observer(RangeObserver *);
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struct Range {
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uint32_t low_address, high_address;
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};
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/*!
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@returns the range of addresses that the video might read from.
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*/
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Range get_memory_access_range();
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private:
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DeferredQueue<HalfCycles> deferrer_;
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Outputs::CRT::CRT crt_;
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RangeObserver *range_observer_ = nullptr;
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uint16_t raw_palette_[16];
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uint16_t palette_[16];
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int base_address_ = 0;
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int previous_base_address_ = 0;
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int current_address_ = 0;
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uint16_t *ram_ = nullptr;
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int x_ = 0, y_ = 0, next_y_ = 0;
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bool load_ = false;
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int load_base_ = 0;
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uint16_t video_mode_ = 0;
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uint16_t sync_mode_ = 0;
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FieldFrequency field_frequency_ = FieldFrequency::Fifty;
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enum class OutputBpp {
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One, Two, Four
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} output_bpp_ = OutputBpp::Four;
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void update_output_mode();
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struct HorizontalState {
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bool enable = false;
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bool blank = false;
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bool sync = false;
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} horizontal_;
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struct VerticalState {
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bool enable = false;
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bool blank = false;
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enum class SyncSchedule {
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/// No sync events this line.
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None,
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/// Sync should begin during this horizontal line.
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Begin,
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/// Sync should end during this horizontal line.
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End,
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} sync_schedule = SyncSchedule::None;
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bool sync = false;
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} vertical_, next_vertical_;
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LineLength line_length_;
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int data_latch_position_ = 0;
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int data_latch_read_position_ = 0;
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uint16_t data_latch_[128];
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void push_latched_data();
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void reset_fifo();
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/*!
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Provides a target for control over the output video stream, which is considered to be
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a permanently shifting shifter, that you need to reload when appropriate, which can be
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overridden by the blank and sync levels.
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This stream will automatically insert a colour burst.
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*/
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class VideoStream {
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public:
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VideoStream(Outputs::CRT::CRT &crt, uint16_t *palette) : crt_(crt), palette_(palette) {}
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enum class OutputMode {
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Sync, Blank, ColourBurst, Pixels,
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};
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/// Sets the current data format for the shifter. Changes in output BPP flush the shifter.
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void set_bpp(OutputBpp bpp);
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/// Outputs signal of type @c mode for @c duration.
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void output(int duration, OutputMode mode);
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/// Warns the video stream that the border colour, included in the palette that it holds a pointer to,
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/// will change momentarily. This should be called after the relevant @c output() updates, and
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/// is used to help elide border-regio output.
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void will_change_border_colour();
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/// Loads 64 bits into the Shifter. The shifter shifts continuously. If you also declare
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/// a pixels region then whatever is being shifted will reach the display, in a form that
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/// depends on the current output BPP.
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void load(uint64_t value);
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private:
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// The target CRT and the palette to use.
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Outputs::CRT::CRT &crt_;
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uint16_t *palette_ = nullptr;
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// Internal stateful processes.
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void generate(int duration, OutputMode mode, bool is_terminal);
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void flush_border();
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void flush_pixels();
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void shift(int duration);
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void output_pixels(int duration);
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// Internal state that is a function of output intent.
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int duration_ = 0;
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OutputMode output_mode_ = OutputMode::Sync;
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OutputBpp bpp_ = OutputBpp::Four;
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union {
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uint64_t output_shifter_;
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uint32_t shifter_halves_[2];
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};
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// Internal state for handling output serialisation.
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uint16_t *pixel_buffer_ = nullptr;
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int pixel_pointer_ = 0;
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} video_stream_;
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/// Contains copies of the various observeable fields, after the relevant propagation delay.
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struct PublicState {
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bool display_enable = false;
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bool hsync = false;
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bool vsync = false;
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} public_state_;
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friend class ::VideoTester;
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};
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}
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}
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#endif /* Atari_ST_Video_hpp */
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