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Adds the absolute most basic version of in-frame time keeping, to display a white square.

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This commit is contained in:
Thomas Harte 2017-11-27 19:43:33 -05:00
parent d33612def5
commit 7d2adad67e
2 changed files with 81 additions and 10 deletions
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83
Components/9918/9918.cpp
View File

@ -11,7 +11,7 @@
using namespace TI;
TMS9918::TMS9918(Personality p) :
crt_(new Outputs::CRT::CRT(911, 1, Outputs::CRT::DisplayType::NTSC60, 3)) {
crt_(new Outputs::CRT::CRT(342, 1, Outputs::CRT::DisplayType::NTSC60, 4)) {
crt_->set_rgb_sampling_function(
"vec3 rgb_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate)"
"{"
@ -24,8 +24,75 @@ std::shared_ptr<Outputs::CRT::CRT> TMS9918::get_crt() {
}
void TMS9918::run_for(const HalfCycles cycles) {
// TODO: all video output (!)
// As specific as I've been able to get:
// Scanline time is always 227.75 cycles.
// PAL output is 313 lines total. NTSC output is 262 lines total.
// Interrupt is signalled upon entering the lower border.
// Convert to 342 cycles per line; the internal clock is 1.5 times the
// nominal 3.579545 Mhz that I've advertised for this part.
int int_cycles = (cycles.as_int() * 3) + cycles_error_;
cycles_error_ = int_cycles & 3;
int_cycles >>= 2;
//
// Break that down as:
// 26 cycles sync;
while(int_cycles) {
int cycles_left = std::min(342 - column_, int_cycles);
int end_column = std::min(column_ + int_cycles, 342);
if(row_ < 192) {
// Pixels.
if(column_ < 26 && end_column >= 26) {
crt_->output_sync(static_cast<unsigned int>(26));
column_ = 26;
}
if(column_ >= 26 && end_column >= 69) { // TODO: modes other than text
crt_->output_blank(static_cast<unsigned int>(69 - 26));
column_ = 69;
pixel_target_ = crt_->allocate_write_area(256);
}
while(column_ < end_column && column_ < 309) { // TODO: modes other than text
pixel_target_[0] = pixel_target_[1] = pixel_target_[2] = pixel_target_[3] = 0xff;
pixel_target_ += 4;
column_ ++;
}
if(column_ == 309 && end_column > 309) {
crt_->output_data(240, 1); // TODO: modes other than text
}
if(end_column == 342) {
crt_->output_blank(static_cast<unsigned int>(342 - 309));
}
} else if(row_ >= 227 && row_ < 230) { // TODO: don't hard-code NTSC.
// Vertical sync.
crt_->output_sync(static_cast<unsigned int>(cycles_left));
} else {
// Blank.
if(column_ < 26 && end_column >= 26) {
crt_->output_sync(static_cast<unsigned int>(26));
column_ = 26;
}
if(column_ < end_column) {
crt_->output_blank(static_cast<unsigned int>(end_column - column_));
column_ = end_column;
}
}
int_cycles += cycles_left;
column_ = end_column;
if(column_ == 342) {
column_ = 0;
row_ = (row_ + 1) % 262; // TODO: don't hard-code NTSC.
// TODO: consider triggering an interrupt here.
}
}
}
// TODO: as a temporary development measure, memory access below is magically instantaneous. Correct that.
void TMS9918::set_register(int address, uint8_t value) {
// Writes to address 0 are writes to the video RAM. Store
// the value and return.
@ -50,36 +117,36 @@ void TMS9918::set_register(int address, uint8_t value) {
// This is a write to a register.
switch(value & 7) {
case 0:
screen_mode_ = (screen_mode_ & 6) | ((low_write_ & 2) >> 1);
next_screen_mode_ = (next_screen_mode_ & 6) | ((low_write_ & 2) >> 1);
break;
case 1:
blank_screen_ = !!(low_write_ & 0x40);
generate_interrupts_ = !!(low_write_ & 0x20);
screen_mode_ = (screen_mode_ & 1) | ((low_write_ & 0x18) >> 3);
next_screen_mode_ = (screen_mode_ & 1) | ((low_write_ & 0x18) >> 3);
sprites_16x16_ = !!(low_write_ & 0x02);
sprites_magnified_ = !!(low_write_ & 0x01);
reevaluate_interrupts();
break;
case 2:
pattern_name_address_ = (low_write_ & 0xf) << 10;
pattern_name_address_ = static_cast<uint16_t>((low_write_ & 0xf) << 10);
break;
case 3:
colour_table_address_ = low_write_ << 6;
colour_table_address_ = static_cast<uint16_t>(low_write_ << 6);
break;
case 4:
pattern_generator_table_address_ = (low_write_ & 0x07) << 11;
pattern_generator_table_address_ = static_cast<uint16_t>((low_write_ & 0x07) << 11);
break;
case 5:
sprite_attribute_table_address_ = (low_write_ & 0x7f) << 7;
sprite_attribute_table_address_ = static_cast<uint16_t>((low_write_ & 0x7f) << 7);
break;
case 6:
sprite_generator_table_address_ = (low_write_ & 0x07) << 11;
sprite_generator_table_address_ = static_cast<uint16_t>((low_write_ & 0x07) << 11);
break;
case 7:

8
Components/9918/9918.hpp
View File

@ -42,7 +42,7 @@ class TMS9918 {
private:
std::shared_ptr<Outputs::CRT::CRT> crt_;
uint16_t ram_[16384];
uint8_t ram_[16384];
uint16_t ram_pointer_ = 0;
uint8_t read_ahead_buffer_ = 0;
@ -53,7 +53,7 @@ class TMS9918 {
uint8_t low_write_ = 0;
// The various register flags.
int screen_mode_ = 0;
int next_screen_mode_ = 0, screen_mode_ = 0;
bool blank_screen_ = true;
bool sprites_16x16_ = false;
bool sprites_magnified_ = false;
@ -67,6 +67,10 @@ class TMS9918 {
uint8_t background_colour_ = 0;
void reevaluate_interrupts();
int column_ = 0, row_ = 0;
int cycles_error_ = 0;
uint8_t *pixel_target_ = nullptr;
};
};