mirror of
https://github.com/TomHarte/CLK.git
synced 2024-07-04 18:29:40 +00:00
380 lines
12 KiB
C++
380 lines
12 KiB
C++
//
|
||
// CGA.hpp
|
||
// Clock Signal
|
||
//
|
||
// Created by Thomas Harte on 05/12/2023.
|
||
// Copyright © 2023 Thomas Harte. All rights reserved.
|
||
//
|
||
|
||
#ifndef CGA_h
|
||
#define CGA_h
|
||
|
||
#include "../../Components/6845/CRTC6845.hpp"
|
||
#include "../../Outputs/CRT/CRT.hpp"
|
||
#include "../../Machines/Utility/ROMCatalogue.hpp"
|
||
|
||
namespace PCCompatible {
|
||
|
||
// TODO: border colour isn't currently honoured.
|
||
class CGA {
|
||
public:
|
||
CGA() : crtc_(Motorola::CRTC::Personality::HD6845S, outputter_) {}
|
||
|
||
static constexpr uint32_t BaseAddress = 0xb'8000;
|
||
static constexpr auto FontROM = ROM::Name::PCCompatibleCGAFont;
|
||
|
||
void set_source(const uint8_t *ram, std::vector<uint8_t> font) {
|
||
outputter_.ram = ram;
|
||
outputter_.font = font;
|
||
}
|
||
|
||
void run_for(Cycles cycles) {
|
||
// Input rate is the PIT rate of 1,193,182 Hz.
|
||
// CGA is clocked at the real oscillator rate of 14 times that.
|
||
// But there's also an internal divide by 8 to align to the fetch clock.
|
||
full_clock_ += 7 * cycles.as<int>();
|
||
|
||
const int modulo = 4 * outputter_.clock_divider;
|
||
crtc_.run_for(Cycles(full_clock_ / modulo));
|
||
full_clock_ %= modulo;
|
||
}
|
||
|
||
template <int address>
|
||
void write(uint8_t value) {
|
||
switch(address) {
|
||
case 0: case 2: case 4: case 6:
|
||
crtc_.select_register(value);
|
||
break;
|
||
case 1: case 3: case 5: case 7:
|
||
crtc_.set_register(value);
|
||
break;
|
||
|
||
case 0x8: outputter_.set_mode(value); break;
|
||
case 0x9: outputter_.set_colours(value); break;
|
||
}
|
||
}
|
||
|
||
template <int address>
|
||
uint8_t read() {
|
||
switch(address) {
|
||
case 1: case 3: case 5: case 7:
|
||
return crtc_.get_register();
|
||
|
||
case 0xa:
|
||
return
|
||
// b3: 1 => in vsync; 0 => not;
|
||
// b2: 1 => light pen switch is off;
|
||
// b1: 1 => positive edge from light pen has set trigger;
|
||
// b0: 1 => safe to write to VRAM now without causing snow.
|
||
(crtc_.get_bus_state().vsync ? 0b1001 : 0b0000) |
|
||
(crtc_.get_bus_state().hsync ? 0b0001 : 0b0000) |
|
||
0b0100;
|
||
|
||
default: return 0xff;
|
||
}
|
||
}
|
||
|
||
// MARK: - Display type configuration.
|
||
|
||
void set_display_type(Outputs::Display::DisplayType display_type) {
|
||
outputter_.crt.set_display_type(display_type);
|
||
}
|
||
Outputs::Display::DisplayType get_display_type() const {
|
||
return outputter_.crt.get_display_type();
|
||
}
|
||
|
||
// MARK: - Call-ins for ScanProducer.
|
||
|
||
void set_scan_target(Outputs::Display::ScanTarget *scan_target) {
|
||
outputter_.crt.set_scan_target(scan_target);
|
||
}
|
||
|
||
Outputs::Display::ScanStatus get_scaled_scan_status() const {
|
||
return outputter_.crt.get_scaled_scan_status() * 4.0f / (7.0f * 8.0f);
|
||
}
|
||
|
||
private:
|
||
struct CRTCOutputter {
|
||
enum class OutputState {
|
||
Sync, Pixels, Border, ColourBurst
|
||
};
|
||
|
||
CRTCOutputter() :
|
||
crt(910, 8, Outputs::Display::Type::NTSC60, Outputs::Display::InputDataType::Red2Green2Blue2)
|
||
{
|
||
crt.set_visible_area(Outputs::Display::Rect(0.097f, 0.095f, 0.82f, 0.82f));
|
||
crt.set_display_type(Outputs::Display::DisplayType::RGB);
|
||
}
|
||
|
||
void set_mode(uint8_t control) {
|
||
// b5: enable blink
|
||
// b4: 1 => 640x200 graphics
|
||
// b3: video enable
|
||
// b2: 1 => monochrome
|
||
// b1: 1 => 320x200 graphics; 0 => text
|
||
// b0: 1 => 80-column text; 0 => 40
|
||
|
||
control_ = control; // To capture blink, monochrome and video enable bits.
|
||
|
||
if(control & 0x2) {
|
||
mode_ = (control & 0x10) ? Mode::Pixels640 : Mode::Pixels320;
|
||
pixels_per_tick = (mode_ == Mode::Pixels640) ? 16 : 8;
|
||
} else {
|
||
mode_ = Mode::Text;
|
||
pixels_per_tick = 8;
|
||
}
|
||
clock_divider = 1 + !(control & 0x01);
|
||
}
|
||
|
||
void set_colours(uint8_t value) {
|
||
// b5: 320x200 palette.
|
||
if(value & 0x20) {
|
||
palette320[1] = 0b00'10'10;
|
||
palette320[2] = 0b10'00'10;
|
||
palette320[3] = 0b10'10'10;
|
||
} else {
|
||
palette320[1] = 0b00'10'00;
|
||
palette320[2] = 0b10'00'00;
|
||
palette320[3] = 0b10'10'00; // TODO: brown, here and elsewhere.
|
||
}
|
||
|
||
// b4: set 320x200 palette into high intensity.
|
||
if(value & 0x10) {
|
||
palette320[1] |= palette320[1] >> 1;
|
||
palette320[2] |= palette320[2] >> 1;
|
||
palette320[3] |= palette320[3] >> 1;
|
||
}
|
||
|
||
// b3–b0: set background, border, monochrome colour.
|
||
palette320[0] = uint8_t(
|
||
((value & 0x01) << 1) |
|
||
((value & 0x02) << 2) |
|
||
((value & 0x04) << 3)
|
||
);
|
||
if(value & 0x08) {
|
||
palette320[0] |= palette320[0] >> 1;
|
||
}
|
||
palette640[1] = palette320[0];
|
||
}
|
||
|
||
uint8_t control() {
|
||
return control_;
|
||
}
|
||
|
||
void update_hsync(bool new_hsync) {
|
||
if(new_hsync == previous_hsync) {
|
||
cycles_since_hsync += clock_divider;
|
||
} else {
|
||
cycles_since_hsync = 0;
|
||
previous_hsync = new_hsync;
|
||
}
|
||
}
|
||
|
||
OutputState implied_state(const Motorola::CRTC::BusState &state) const {
|
||
OutputState new_state;
|
||
|
||
if(state.hsync || state.vsync) {
|
||
new_state = OutputState::Sync;
|
||
} else if(!state.display_enable || !(control_&0x08)) {
|
||
new_state = OutputState::Border;
|
||
|
||
// TODO: I'm pretty sure this isn't correct for colour burst positioning, though
|
||
// it happens to fool the particular CRT I've implemented.
|
||
if(!(control_&4) && cycles_since_hsync <= 4) {
|
||
new_state = OutputState::ColourBurst;
|
||
}
|
||
} else {
|
||
new_state = OutputState::Pixels;
|
||
}
|
||
|
||
return new_state;
|
||
}
|
||
|
||
void perform_bus_cycle_phase1(const Motorola::CRTC::BusState &state) {
|
||
// Determine new output state.
|
||
update_hsync(state.hsync);
|
||
const OutputState new_state = implied_state(state);
|
||
|
||
// Upon either a state change or just having accumulated too much local time...
|
||
if(new_state != output_state || active_pixels_per_tick != pixels_per_tick || active_clock_divider != clock_divider || count > 912) {
|
||
// (1) flush preexisting state.
|
||
if(count) {
|
||
switch(output_state) {
|
||
case OutputState::Sync: crt.output_sync(count * active_clock_divider); break;
|
||
case OutputState::Border: crt.output_blank(count * active_clock_divider); break;
|
||
case OutputState::ColourBurst: crt.output_colour_burst(count * active_clock_divider, 0); break;
|
||
case OutputState::Pixels: flush_pixels(); break;
|
||
}
|
||
}
|
||
|
||
// (2) adopt new state.
|
||
output_state = new_state;
|
||
active_pixels_per_tick = pixels_per_tick;
|
||
active_clock_divider = clock_divider;
|
||
count = 0;
|
||
}
|
||
|
||
// Collect pixels if applicable.
|
||
if(output_state == OutputState::Pixels) {
|
||
if(!pixels) {
|
||
pixel_pointer = pixels = crt.begin_data(DefaultAllocationSize);
|
||
|
||
// Flush any period where pixels weren't recorded due to back pressure.
|
||
if(pixels && count) {
|
||
crt.output_blank(count * active_clock_divider);
|
||
count = 0;
|
||
}
|
||
}
|
||
|
||
if(pixels) {
|
||
if(state.cursor) {
|
||
std::fill(pixel_pointer, pixel_pointer + pixels_per_tick, 0x3f); // i.e. white.
|
||
} else {
|
||
if(mode_ == Mode::Text) {
|
||
serialise_text(state);
|
||
} else {
|
||
serialise_pixels(state);
|
||
}
|
||
}
|
||
pixel_pointer += active_pixels_per_tick;
|
||
}
|
||
}
|
||
|
||
// Advance.
|
||
count += 8;
|
||
|
||
// Output pixel row prematurely if storage is exhausted.
|
||
if(output_state == OutputState::Pixels && pixel_pointer == pixels + DefaultAllocationSize) {
|
||
flush_pixels();
|
||
count = 0;
|
||
}
|
||
}
|
||
void perform_bus_cycle_phase2(const Motorola::CRTC::BusState &) {}
|
||
|
||
void flush_pixels() {
|
||
crt.output_data(count * active_clock_divider, size_t((count * active_pixels_per_tick) / 8));
|
||
pixels = pixel_pointer = nullptr;
|
||
}
|
||
|
||
void serialise_pixels(const Motorola::CRTC::BusState &state) {
|
||
// This is what I think is happenings:
|
||
//
|
||
// Refresh address is still shifted left one and two bytes are fetched, just as if it were
|
||
// character code + attributes except that these are two bytes worth of graphics.
|
||
//
|
||
// Meanwhile, row address is used to invent a 15th address line.
|
||
const auto base_address =
|
||
((state.refresh_address & 0xfff) << 1) +
|
||
((state.row_address & 1) << 13);
|
||
const uint8_t bitmap[] = {
|
||
ram[base_address],
|
||
ram[base_address + 1],
|
||
};
|
||
|
||
if(mode_ == Mode::Pixels320) {
|
||
pixel_pointer[0] = palette320[(bitmap[0] & 0xc0) >> 6];
|
||
pixel_pointer[1] = palette320[(bitmap[0] & 0x30) >> 4];
|
||
pixel_pointer[2] = palette320[(bitmap[0] & 0x0c) >> 2];
|
||
pixel_pointer[3] = palette320[(bitmap[0] & 0x03) >> 0];
|
||
pixel_pointer[4] = palette320[(bitmap[1] & 0xc0) >> 6];
|
||
pixel_pointer[5] = palette320[(bitmap[1] & 0x30) >> 4];
|
||
pixel_pointer[6] = palette320[(bitmap[1] & 0x0c) >> 2];
|
||
pixel_pointer[7] = palette320[(bitmap[1] & 0x03) >> 0];
|
||
} else {
|
||
pixel_pointer[0x0] = palette640[(bitmap[0] & 0x80) >> 7];
|
||
pixel_pointer[0x1] = palette640[(bitmap[0] & 0x40) >> 6];
|
||
pixel_pointer[0x2] = palette640[(bitmap[0] & 0x20) >> 5];
|
||
pixel_pointer[0x3] = palette640[(bitmap[0] & 0x10) >> 4];
|
||
pixel_pointer[0x4] = palette640[(bitmap[0] & 0x08) >> 3];
|
||
pixel_pointer[0x5] = palette640[(bitmap[0] & 0x04) >> 2];
|
||
pixel_pointer[0x6] = palette640[(bitmap[0] & 0x02) >> 1];
|
||
pixel_pointer[0x7] = palette640[(bitmap[0] & 0x01) >> 0];
|
||
pixel_pointer[0x8] = palette640[(bitmap[1] & 0x80) >> 7];
|
||
pixel_pointer[0x9] = palette640[(bitmap[1] & 0x40) >> 6];
|
||
pixel_pointer[0xa] = palette640[(bitmap[1] & 0x20) >> 5];
|
||
pixel_pointer[0xb] = palette640[(bitmap[1] & 0x10) >> 4];
|
||
pixel_pointer[0xc] = palette640[(bitmap[1] & 0x08) >> 3];
|
||
pixel_pointer[0xd] = palette640[(bitmap[1] & 0x04) >> 2];
|
||
pixel_pointer[0xe] = palette640[(bitmap[1] & 0x02) >> 1];
|
||
pixel_pointer[0xf] = palette640[(bitmap[1] & 0x01) >> 0];
|
||
}
|
||
}
|
||
|
||
void serialise_text(const Motorola::CRTC::BusState &state) {
|
||
const uint8_t attributes = ram[((state.refresh_address << 1) + 1) & 0x3fff];
|
||
const uint8_t glyph = ram[((state.refresh_address << 1) + 0) & 0x3fff];
|
||
const uint8_t row = font[(glyph * 8) + state.row_address];
|
||
|
||
uint8_t colours[2] = {
|
||
uint8_t(((attributes & 0x40) >> 1) | ((attributes & 0x20) >> 2) | ((attributes & 0x10) >> 3)),
|
||
uint8_t(((attributes & 0x04) << 3) | ((attributes & 0x02) << 2) | ((attributes & 0x01) << 1)),
|
||
};
|
||
|
||
// Apply foreground intensity.
|
||
if(attributes & 0x08) {
|
||
colours[1] |= colours[1] >> 1;
|
||
}
|
||
|
||
// Apply blink or background intensity.
|
||
if(control_ & 0x20) {
|
||
if((attributes & 0x80) && (state.field_count & 16)) {
|
||
std::swap(colours[0], colours[1]);
|
||
}
|
||
} else {
|
||
if(attributes & 0x80) {
|
||
colours[0] |= colours[0] >> 1;
|
||
}
|
||
}
|
||
|
||
// Draw according to ROM contents.
|
||
pixel_pointer[0] = (row & 0x80) ? colours[1] : colours[0];
|
||
pixel_pointer[1] = (row & 0x40) ? colours[1] : colours[0];
|
||
pixel_pointer[2] = (row & 0x20) ? colours[1] : colours[0];
|
||
pixel_pointer[3] = (row & 0x10) ? colours[1] : colours[0];
|
||
pixel_pointer[4] = (row & 0x08) ? colours[1] : colours[0];
|
||
pixel_pointer[5] = (row & 0x04) ? colours[1] : colours[0];
|
||
pixel_pointer[6] = (row & 0x02) ? colours[1] : colours[0];
|
||
pixel_pointer[7] = (row & 0x01) ? colours[1] : colours[0];
|
||
}
|
||
|
||
Outputs::CRT::CRT crt;
|
||
static constexpr size_t DefaultAllocationSize = 320;
|
||
|
||
// Current output stream.
|
||
uint8_t *pixels = nullptr;
|
||
uint8_t *pixel_pointer = nullptr;
|
||
int active_pixels_per_tick = 8;
|
||
int active_clock_divider = 1;
|
||
|
||
// Source data.
|
||
const uint8_t *ram = nullptr;
|
||
std::vector<uint8_t> font;
|
||
|
||
// CRTC state tracking, for CRT serialisation.
|
||
OutputState output_state = OutputState::Sync;
|
||
int count = 0;
|
||
|
||
bool previous_hsync = false;
|
||
int cycles_since_hsync = 0;
|
||
|
||
// Current Programmer-set parameters.
|
||
int clock_divider = 1;
|
||
int pixels_per_tick = 8;
|
||
uint8_t control_ = 0;
|
||
enum class Mode {
|
||
Pixels640, Pixels320, Text,
|
||
} mode_ = Mode::Text;
|
||
|
||
uint8_t palette320[4]{};
|
||
uint8_t palette640[2]{};
|
||
|
||
} outputter_;
|
||
Motorola::CRTC::CRTC6845<CRTCOutputter, Motorola::CRTC::CursorType::MDA> crtc_;
|
||
|
||
int full_clock_ = 0;
|
||
};
|
||
|
||
}
|
||
|
||
#endif /* CGA_h */
|