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403 lines
11 KiB
C++
403 lines
11 KiB
C++
//
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// 9918.cpp
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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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#include "9918.hpp"
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using namespace TI;
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namespace {
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const uint32_t palette_pack(uint8_t r, uint8_t g, uint8_t b) {
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uint32_t result = 0;
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uint8_t *result_ptr = reinterpret_cast<uint8_t *>(&result);
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result_ptr[0] = r;
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result_ptr[1] = g;
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result_ptr[2] = b;
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result_ptr[3] = 0;
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return result;
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}
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const uint32_t palette[16] = {
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palette_pack(0, 0, 0),
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palette_pack(0, 0, 0),
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palette_pack(90, 201, 81),
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palette_pack(149, 231, 133),
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palette_pack(113, 104, 183),
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palette_pack(146, 132, 255),
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palette_pack(200, 114, 89),
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palette_pack(115, 222, 255),
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palette_pack(238, 124, 90),
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palette_pack(255, 166, 132),
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palette_pack(219, 232, 92),
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palette_pack(240, 247, 143),
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palette_pack(78, 176, 63),
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palette_pack(202, 118, 216),
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palette_pack(233, 233, 233),
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palette_pack(255, 255, 255)
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};
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}
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TMS9918::TMS9918(Personality p) :
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crt_(new Outputs::CRT::CRT(342, 1, Outputs::CRT::DisplayType::NTSC60, 4)) {
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crt_->set_rgb_sampling_function(
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"vec3 rgb_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate)"
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"{"
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"return texture(sampler, coordinate).rgb / vec3(255.0);"
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"}");
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crt_->set_output_device(Outputs::CRT::OutputDevice::Monitor);
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}
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std::shared_ptr<Outputs::CRT::CRT> TMS9918::get_crt() {
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return crt_;
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}
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void TMS9918::run_for(const HalfCycles cycles) {
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// As specific as I've been able to get:
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// Scanline time is always 227.75 cycles.
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// PAL output is 313 lines total. NTSC output is 262 lines total.
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// Interrupt is signalled upon entering the lower border.
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// Keep a count of cycles separate from internal counts to avoid
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// potential errors mapping back and forth.
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half_cycles_into_frame_ = (half_cycles_into_frame_ + cycles) % HalfCycles(frame_lines_ * 228 * 2);
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// Convert to 342 cycles per line; the internal clock is 1.5 times the
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// nominal 3.579545 Mhz that I've advertised for this part.
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int int_cycles = (cycles.as_int() * 3) + cycles_error_;
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cycles_error_ = int_cycles & 7;
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int_cycles >>= 3;
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if(!int_cycles) return;
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//
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// Break that down as:
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// 26 cycles sync;
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while(int_cycles) {
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int cycles_left = std::min(342 - column_, int_cycles);
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column_ += cycles_left;
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int_cycles -= cycles_left;
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if(row_ < 192 && !blank_screen_) {
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// ------------------------
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// Perform memory accesses.
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// ------------------------
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const int access_slot = column_ >> 1; // There are only 171 available memory accesses per line.
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switch(line_mode_) {
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case LineMode::Text:
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while(access_pointer_ < access_slot) {
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if(access_pointer_ < 29) {
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access_pointer_ = std::min(29, access_slot);
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}
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if(access_pointer_ >= 29) {
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int row_base = pattern_name_address_ + (row_ >> 3) * 40;
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int character_column = (access_pointer_ - 29) / 3;
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const int end = std::min(149, access_slot);
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while(access_pointer_ < end) {
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switch(access_pointer_%3) {
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case 0:
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pattern_buffer_[character_column] = ram_[pattern_generator_table_address_ + (pattern_name_ << 3) + (row_ & 7)];
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character_column++;
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break;
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case 1: break; // TODO: CPU access.
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case 2:
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pattern_name_ = ram_[row_base + character_column];
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break;
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}
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access_pointer_++;
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}
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}
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if(access_pointer_ >= 149) {
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access_pointer_ = access_slot;
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}
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}
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break;
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case LineMode::Character:
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while(access_pointer_ < access_slot) {
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if(access_pointer_ < 26) {
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access_pointer_ = std::min(26, access_slot);
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}
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if(access_pointer_ >= 26) {
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int end = std::min(154, access_slot);
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int row_base = pattern_name_address_;
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int pattern_base = pattern_generator_table_address_;
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int colour_base = colour_table_address_;
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int colour_shift = 3;
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if(screen_mode_ == 1) {
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pattern_base &= 0x2000 | ((row_ & 0xc0) << 5);
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colour_base &= 0x2000 | ((row_ & 0xc0) << 5);
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colour_shift = 0;
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}
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row_base += (row_ << 2)&~31;
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// TODO: optimise this mess.
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while(access_pointer_ < end) {
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int character_column = ((access_pointer_ - 26) >> 2);
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switch(access_pointer_&3) {
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case 0:
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pattern_name_ = ram_[row_base + character_column];
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break;
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case 1: break; // TODO: sprites / CPU access.
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case 2:
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colour_buffer_[character_column] = ram_[colour_base + (pattern_name_ >> colour_shift)];
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break;
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case 3:
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pattern_buffer_[character_column] = ram_[pattern_base + (pattern_name_ << 3) + (row_ & 7)];
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break;
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}
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access_pointer_++;
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}
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}
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if(access_pointer_ >= 154) {
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access_pointer_ = access_slot;
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}
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}
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break;
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}
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// --------------------
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// End memory accesses.
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// --------------------
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// ----------------------
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// Output horizontal sync
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// ----------------------
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if(!output_column_ && column_ >= 26) {
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crt_->output_sync(static_cast<unsigned int>(26));
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output_column_ = 26;
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}
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// --------------------------
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// TODO: output colour burst.
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// --------------------------
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// -------------------
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// Output left border.
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// -------------------
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if(output_column_ >= 26) {
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int pixels_end = std::min(first_pixel_column_, column_);
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if(output_column_ < pixels_end) {
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output_border(pixels_end - output_column_);
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output_column_ = pixels_end;
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// Grab a pointer for drawing pixels to, if the moment has arrived.
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if(pixels_end == first_pixel_column_) {
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pixel_target_ = reinterpret_cast<uint32_t *>(crt_->allocate_write_area(static_cast<unsigned int>(first_right_border_column_ - first_pixel_column_)));
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}
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}
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}
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// --------------
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// Output pixels.
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// --------------
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if(output_column_ >= first_pixel_column_) {
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int pixels_end = std::min(first_right_border_column_, column_);
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if(output_column_ < pixels_end) {
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switch(line_mode_) {
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case LineMode::Text:
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while(output_column_ < pixels_end) {
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const int base = (output_column_ - first_pixel_column_);
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const int address = base / 6;
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const uint8_t pattern = pattern_buffer_[address] << (base % 6);
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*pixel_target_ = (pattern&0x80) ? palette[text_colour_] : palette[background_colour_];
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pixel_target_ ++;
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output_column_ ++;
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}
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break;
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case LineMode::Character:
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while(output_column_ < pixels_end) {
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int base = (output_column_ - first_pixel_column_);
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int address = base >> 3;
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uint8_t colour = colour_buffer_[address];
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uint8_t pattern = pattern_buffer_[address];
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pattern >>= ((base&7)^7);
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*pixel_target_ = (pattern&1) ? palette[colour >> 4] : palette[colour & 15];
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pixel_target_ ++;
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output_column_ ++;
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}
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break;
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}
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if(output_column_ == first_right_border_column_) {
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crt_->output_data(static_cast<unsigned int>(first_right_border_column_ - first_pixel_column_), 1);
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pixel_target_ = nullptr;
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}
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}
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}
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// --------------------
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// Output right border.
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// --------------------
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if(output_column_ >= first_right_border_column_) {
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output_border(column_ - output_column_);
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output_column_ = column_;
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}
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} else if(row_ >= first_vsync_line_ && row_ < first_vsync_line_+3) {
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// Vertical sync.
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if(column_ == 342) {
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crt_->output_sync(static_cast<unsigned int>(342));
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}
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} else {
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// Blank.
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if(!output_column_ && column_ >= 26) {
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crt_->output_sync(static_cast<unsigned int>(26));
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output_column_ = 26;
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}
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if(output_column_ >= 26) {
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output_border(column_ - output_column_);
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output_column_ = column_;
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}
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}
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if(column_ == 342) {
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access_pointer_ = column_ = output_column_ = 0;
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row_ = (row_ + 1) % frame_lines_;
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if(row_ == 192) status_ |= 0x80;
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screen_mode_ = next_screen_mode_;
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blank_screen_ = next_blank_screen_;
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switch(screen_mode_) {
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case 2:
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line_mode_ = LineMode::Text;
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first_pixel_column_ = 69;
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first_right_border_column_ = 309;
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break;
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default:
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line_mode_ = LineMode::Character;
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first_pixel_column_ = 63;
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first_right_border_column_ = 319;
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break;
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}
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}
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}
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}
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void TMS9918::output_border(int cycles) {
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pixel_target_ = reinterpret_cast<uint32_t *>(crt_->allocate_write_area(1));
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if(pixel_target_) *pixel_target_ = palette[background_colour_];
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crt_->output_level(static_cast<unsigned int>(cycles));
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}
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// TODO: as a temporary development measure, memory access below is magically instantaneous. Correct that.
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void TMS9918::set_register(int address, uint8_t value) {
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// Writes to address 0 are writes to the video RAM. Store
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// the value and return.
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if(!(address & 1)) {
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write_phase_ = false;
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read_ahead_buffer_ = value;
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ram_[ram_pointer_ & 16383] = value;
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ram_pointer_++;
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return;
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}
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// Writes to address 1 are performed in pairs; if this is the
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// low byte of a value, store it and wait for the high byte.
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if(!write_phase_) {
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low_write_ = value;
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write_phase_ = true;
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return;
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}
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write_phase_ = false;
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if(value & 0x80) {
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// This is a write to a register.
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switch(value & 7) {
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case 0:
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next_screen_mode_ = (next_screen_mode_ & 6) | ((low_write_ & 2) >> 1);
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printf("NSM: %02x\n", next_screen_mode_);
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break;
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case 1:
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next_blank_screen_ = !(low_write_ & 0x40);
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generate_interrupts_ = !!(low_write_ & 0x20);
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next_screen_mode_ = (next_screen_mode_ & 1) | ((low_write_ & 0x18) >> 3);
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sprites_16x16_ = !!(low_write_ & 0x02);
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sprites_magnified_ = !!(low_write_ & 0x01);
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printf("NSM: %02x\n", next_screen_mode_);
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break;
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case 2:
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pattern_name_address_ = static_cast<uint16_t>((low_write_ & 0xf) << 10);
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break;
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case 3:
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colour_table_address_ = static_cast<uint16_t>(low_write_ << 6);
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break;
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case 4:
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pattern_generator_table_address_ = static_cast<uint16_t>((low_write_ & 0x07) << 11);
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break;
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case 5:
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sprite_attribute_table_address_ = static_cast<uint16_t>((low_write_ & 0x7f) << 7);
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break;
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case 6:
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sprite_generator_table_address_ = static_cast<uint16_t>((low_write_ & 0x07) << 11);
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break;
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case 7:
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text_background_colour_ = low_write_;
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text_colour_ = low_write_ >> 4;
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background_colour_ = low_write_ & 0xf;
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break;
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}
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} else {
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// This is a write to the RAM pointer.
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ram_pointer_ = static_cast<uint16_t>(low_write_ | (value << 8));
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if(!(value & 0x40)) {
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// Officially a 'read' set, so perform lookahead.
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read_ahead_buffer_ = ram_[ram_pointer_ & 16383];
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ram_pointer_++;
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}
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}
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}
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uint8_t TMS9918::get_register(int address) {
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write_phase_ = false;
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// Reads from address 0 read video RAM, via the read-ahead buffer.
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if(!(address & 1)) {
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uint8_t result = read_ahead_buffer_;
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read_ahead_buffer_ = ram_[ram_pointer_ & 16383];
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ram_pointer_++;
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return result;
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}
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// Reads from address 1 get the status register;
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uint8_t result = status_;
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status_ &= ~(0x80 | 0x20);
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return result;
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}
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HalfCycles TMS9918::get_time_until_interrupt() {
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if(!generate_interrupts_) return HalfCycles(-1);
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if(get_interrupt_line()) return HalfCycles(-1);
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const int half_cycles_per_frame = frame_lines_ * 228 * 2;
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int half_cycles_remaining = (192 * 228 * 2 + half_cycles_per_frame - half_cycles_into_frame_.as_int()) % half_cycles_per_frame;
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return HalfCycles(half_cycles_remaining);
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}
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bool TMS9918::get_interrupt_line() {
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return (status_ & 0x80) && generate_interrupts_;
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}
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