mirror of https://github.com/TomHarte/CLK.git
129 lines
3.7 KiB
C++
129 lines
3.7 KiB
C++
//
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// 9918.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 25/11/2017.
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// Copyright 2017 Thomas Harte. All rights reserved.
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//
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#pragma once
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#include "../../Outputs/CRT/CRT.hpp"
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#include "../../ClockReceiver/ClockReceiver.hpp"
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#include <cstdint>
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namespace TI::TMS {
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enum Personality {
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TMS9918A, // includes the 9928 and 9929; set TV standard and output device as desired.
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// Yamaha extensions.
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V9938,
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V9958,
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// Sega extensions.
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SMSVDP,
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SMS2VDP,
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GGVDP,
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MDVDP,
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};
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enum class TVStandard {
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/*! i.e. 50Hz output at around 312.5 lines/field */
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PAL,
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/*! i.e. 60Hz output at around 262.5 lines/field */
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NTSC
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};
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}
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#include "Implementation/9918Base.hpp"
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namespace TI::TMS {
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/*!
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Provides emulation of the TMS9918a, TMS9928 and TMS9929. Likely in the future to be the
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vessel for emulation of sufficiently close derivatives, such as the Master System VDP.
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The TMS9918 and descendants are video display generators that own their own RAM, making it
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accessible through an implicitly-timed register interface, and (depending on model) can generate
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PAL and NTSC component and composite video.
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These chips have only one non-on-demand interaction with the outside world: an interrupt line.
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See get_time_until_interrupt and get_interrupt_line for asynchronous operation options.
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*/
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template <Personality personality> class TMS9918: private Base<personality> {
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public:
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/*! Constructs an instance of the VDP that behaves according to the templated personality. */
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TMS9918();
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/*! Sets the TV standard for this TMS, if that is hard-coded in hardware. */
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void set_tv_standard(TVStandard standard);
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/*! Sets the scan target this TMS will post content to. */
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void set_scan_target(Outputs::Display::ScanTarget *);
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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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/*! Sets the type of CRT display. */
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void set_display_type(Outputs::Display::DisplayType);
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/*! Gets the type of CRT display. */
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Outputs::Display::DisplayType get_display_type() const;
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/*!
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Runs the VDP for the number of cycles indicate; the input clock rate is implicitly assumed.
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For everything except the Mega Drive VDP:
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* the input clock rate should be 3579545 Hz, the NTSC colour clock rate.
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For the Mega Drive:
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* the input clock rate should be around 7.6MHz; 15/7ths of the NTSC colour
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clock rate for NTSC output and 12/7ths of the PAL colour clock rate for PAL output.
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*/
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void run_for(const HalfCycles cycles);
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/*! Sets a register value. */
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void write(int address, uint8_t value);
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/*! Gets a register value. */
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uint8_t read(int address);
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/*! Gets the current scan line; provided by the Sega VDPs only. */
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uint8_t get_current_line() const;
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/*! Gets the current latched horizontal counter; provided by the Sega VDPs only. */
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uint8_t get_latched_horizontal_counter() const;
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/*! Latches the current horizontal counter. */
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void latch_horizontal_counter();
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/*!
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Returns the amount of time until @c get_interrupt_line would next change if
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there are no interceding calls to @c write or to @c read.
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If get_interrupt_line is true now of if get_interrupt_line would
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never return true, returns HalfCycles::max().
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*/
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HalfCycles next_sequence_point() const;
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/*!
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Returns the amount of time until the nominated line interrupt position is
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reached on line @c line. If no line interrupt position is defined for
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this VDP, returns the time until the 'beginning' of that line, whatever
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that may mean.
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@line is relative to the first pixel line of the display and may be negative.
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*/
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HalfCycles get_time_until_line(int line);
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/*!
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@returns @c true if the interrupt line is currently active; @c false otherwise.
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*/
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bool get_interrupt_line() const;
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};
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}
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