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265 lines
8.3 KiB
C++
265 lines
8.3 KiB
C++
//
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// Video.cpp
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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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#include "Video.hpp"
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#include "../../Outputs/Log.hpp"
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#include <algorithm>
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using namespace Atari::ST;
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namespace {
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struct ModeParams {
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const int lines_per_frame;
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const int first_video_line;
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const int final_video_line;
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const int line_length;
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const int end_of_blank;
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const int start_of_display_enable;
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const int end_of_display_enable;
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const int start_of_output;
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const int end_of_output;
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const int start_of_blank;
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const int start_of_hsync;
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const int end_of_hsync;
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} modes[3] = {
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{313, 56, 256, 1024, 64, 116, 116+640, 116+48, 116+48+640, 904, 928, 1008 },
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{},
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{}
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};
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const ModeParams &mode_params_for_mode() {
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// TODO: rest of potential combinations, and accept mode as a paramter.
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return modes[0];
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}
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}
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Video::Video() :
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crt_(1024, 1, Outputs::Display::Type::PAL50, Outputs::Display::InputDataType::Red4Green4Blue4) {
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}
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void Video::set_ram(uint16_t *ram) {
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ram_ = ram;
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}
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void Video::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
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crt_.set_scan_target(scan_target);
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}
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void Video::run_for(HalfCycles duration) {
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int integer_duration = int(duration.as_integral());
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const auto mode_params = mode_params_for_mode();
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#define Period(lower, upper, type) \
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if(x >= lower && x < upper) { \
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const auto target = std::min(upper, final_x); \
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type(target - x); \
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x = target; \
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}
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// TODO: the below is **way off**. The real hardware does what you'd expect with ongoing state and
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// exact equality tests. Fixes to come.
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while(integer_duration) {
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const int final_x = std::min(x + integer_duration, mode_params.line_length);
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integer_duration -= (final_x - x);
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if(y >= mode_params.first_video_line && y < mode_params.final_video_line) {
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// TODO: Prior to output: collect all necessary data, obeying start_of_display_enable and end_of_display_enable.
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Period(0, mode_params.end_of_blank, crt_.output_blank);
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Period(mode_params.end_of_blank, mode_params.start_of_output, output_border);
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if(x >= mode_params.start_of_output && x < mode_params.end_of_output) {
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if(x == mode_params.start_of_output) {
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// TODO: resolutions other than 320.
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pixel_pointer_ = reinterpret_cast<uint16_t *>(crt_.begin_data(320));
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}
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const auto target = std::min(mode_params.end_of_output, final_x);
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while(x < target) {
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if(!(x&31) && pixel_pointer_) {
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// TODO: RAM sizes other than 512kb.
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uint16_t source[4] = {
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ram_[(current_address_ + 0) & 262143],
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ram_[(current_address_ + 1) & 262143],
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ram_[(current_address_ + 2) & 262143],
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ram_[(current_address_ + 3) & 262143],
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};
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current_address_ += 4;
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for(int c = 0; c < 16; ++c) {
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*pixel_pointer_ = palette_[
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((source[3] >> 12) & 0x8) |
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((source[2] >> 13) & 0x4) |
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((source[1] >> 14) & 0x2) |
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((source[0] >> 15) & 0x1)
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];
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source[0] <<= 1;
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source[1] <<= 1;
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source[2] <<= 1;
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source[3] <<= 1;
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++pixel_pointer_;
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}
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}
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++x;
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}
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if(x == mode_params.end_of_output) {
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crt_.output_data(mode_params.end_of_output - mode_params.start_of_output, 320);
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pixel_pointer_ = nullptr;
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}
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}
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Period(mode_params.end_of_output, mode_params.start_of_blank, output_border);
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Period(mode_params.start_of_blank, mode_params.start_of_hsync, crt_.output_blank);
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Period(mode_params.start_of_hsync, mode_params.end_of_hsync, crt_.output_sync);
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Period(mode_params.end_of_hsync, mode_params.line_length, crt_.output_blank);
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} else {
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// Hard code the first three lines as vertical sync.
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if(y < 3) {
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Period(0, mode_params.start_of_hsync, crt_.output_sync);
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Period(mode_params.start_of_hsync, mode_params.end_of_hsync, crt_.output_blank);
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Period(mode_params.end_of_hsync, mode_params.line_length, crt_.output_sync);
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} else {
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Period(0, mode_params.end_of_blank, crt_.output_blank);
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Period(mode_params.end_of_blank, mode_params.start_of_blank, output_border);
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Period(mode_params.start_of_blank, mode_params.start_of_hsync, crt_.output_blank);
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Period(mode_params.start_of_hsync, mode_params.end_of_hsync, crt_.output_sync);
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Period(mode_params.end_of_hsync, mode_params.line_length, crt_.output_blank);
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}
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}
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if(x == mode_params.line_length) {
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x = 0;
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y = (y + 1) % mode_params.lines_per_frame;
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if(!y)
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current_address_ = base_address_ >> 1;
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}
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}
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#undef Period
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}
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void Video::output_border(int duration) {
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uint16_t *colour_pointer = reinterpret_cast<uint16_t *>(crt_.begin_data(1));
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if(colour_pointer) *colour_pointer = palette_[0];
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crt_.output_level(duration);
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}
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bool Video::hsync() {
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const auto mode_params = mode_params_for_mode();
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return x >= mode_params.start_of_hsync && x < mode_params.end_of_hsync;
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}
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bool Video::vsync() {
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return y < 3;
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}
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bool Video::display_enabled() {
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const auto mode_params = mode_params_for_mode();
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return y >= mode_params.first_video_line && y < mode_params.final_video_line && x >= mode_params.start_of_display_enable && x < mode_params.end_of_display_enable;
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}
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HalfCycles Video::get_next_sequence_point() {
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// The next hsync transition will occur either this line or the next.
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const auto mode_params = mode_params_for_mode();
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HalfCycles cycles_until_hsync;
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if(x < mode_params.start_of_hsync) {
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cycles_until_hsync = HalfCycles(mode_params.start_of_hsync - x);
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} else if(x < mode_params.end_of_hsync) {
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cycles_until_hsync = HalfCycles(mode_params.end_of_hsync - x);
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} else {
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cycles_until_hsync = HalfCycles(mode_params.start_of_hsync + mode_params.line_length - x);
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}
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// The next vsync transition depends purely on the current y.
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HalfCycles cycles_until_vsync;
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if(y < 3) {
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cycles_until_vsync = HalfCycles(mode_params.line_length - x + (2 - y)*mode_params.line_length);
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} else {
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cycles_until_vsync = HalfCycles(mode_params.line_length - x + (mode_params.lines_per_frame - 1 - y)*mode_params.line_length);
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}
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// The next display enable transition will occur only in the visible area.
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HalfCycles cycles_until_display_enable;
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if(display_enabled()) {
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cycles_until_display_enable = HalfCycles(mode_params.end_of_display_enable - x);
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} else {
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const auto horizontal_cycles = mode_params.start_of_display_enable - x;
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int vertical_lines = 0;
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if(y < mode_params.first_video_line) {
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vertical_lines = mode_params.first_video_line - y;
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} else if(y >= mode_params.final_video_line ) {
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vertical_lines = mode_params.first_video_line + mode_params.lines_per_frame - y;
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}
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if(horizontal_cycles < 0) ++vertical_lines;
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cycles_until_display_enable = HalfCycles(horizontal_cycles + vertical_lines * mode_params.line_length);
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}
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// Determine the minimum of the three
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if(cycles_until_hsync < cycles_until_vsync && cycles_until_hsync < cycles_until_display_enable) {
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return cycles_until_hsync;
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} else {
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return (cycles_until_vsync < cycles_until_display_enable) ? cycles_until_vsync : cycles_until_display_enable;
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}
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}
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// MARK: - IO dispatch
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uint16_t Video::read(int address) {
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LOG("[Video] read " << PADHEX(2) << (address & 0x3f));
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address &= 0x3f;
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switch(address) {
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default:
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break;
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case 0x00: return uint16_t(0xff00 | (base_address_ >> 16));
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case 0x01: return uint16_t(0xff00 | (base_address_ >> 8));
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case 0x02: return uint16_t(0xff00 | (current_address_ >> 16));
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case 0x03: return uint16_t(0xff00 | (current_address_ >> 8));
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case 0x04: return uint16_t(0xff00 | (current_address_));
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case 0x30: return video_mode_ | 0xfcff;
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}
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return 0xff;
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}
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void Video::write(int address, uint16_t value) {
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LOG("[Video] write " << PADHEX(2) << int(value) << " to " << PADHEX(2) << (address & 0x3f));
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address &= 0x3f;
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switch(address) {
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default: break;
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// Start address.
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case 0x00: base_address_ = (base_address_ & 0x00ffff) | ((value & 0xff) << 16); break;
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case 0x01: base_address_ = (base_address_ & 0xff00ff) | ((value & 0xff) << 8); break;
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// Mode.
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case 0x30: video_mode_ = value; break;
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// Palette.
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case 0x20: case 0x21: case 0x22: case 0x23:
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case 0x24: case 0x25: case 0x26: case 0x27:
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case 0x28: case 0x29: case 0x2a: case 0x2b:
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case 0x2c: case 0x2d: case 0x2e: case 0x2f: {
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uint8_t *const entry = reinterpret_cast<uint8_t *>(&palette_[address - 0x20]);
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entry[0] = uint8_t((value & 0x700) >> 7);
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entry[1] = uint8_t((value & 0x77) << 1);
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} break;
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}
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}
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