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I'm sure it's not going to be this easy, but this is a genuine attempt at full horizontal and vertical timing.

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This commit is contained in:
Thomas Harte 2017-07-31 22:01:54 -04:00
parent e28829bd1b
commit cb0dc7b434
1 changed files with 85 additions and 2 deletions
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87
Components/6845/CRTC6845.hpp
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@ -33,8 +33,82 @@ template <class T> class CRTC6845 {
void run_for(Cycles cycles) {
int cyles_remaining = cycles.as_int();
while(cyles_remaining--) {
// TODO: update state (!)
// check for end of horizontal sync
if(hsync_down_counter_) {
hsync_down_counter_--;
if(!hsync_down_counter_) {
bus_state_.hsync = false;
}
}
// advance horizontal counter
character_counter_++;
// check for start of horizontal sync
if(character_counter_ == registers_[2]) {
hsync_down_counter_ = registers_[3] & 15;
if(hsync_down_counter_) bus_state_.hsync = true;
}
// check for end of visible characters
if(character_counter_ == registers_[1]) {
character_is_visible_ = false;
}
// check for end-of-line
if(character_counter_ == registers_[0]+1) {
character_counter_ = 0;
character_is_visible_ = true;
// check for end of vertical sync
if(vsync_down_counter_) {
vsync_down_counter_--;
if(!vsync_down_counter_) {
bus_state_.vsync = false;
}
}
if(is_in_adjustment_period_) {
line_counter_++;
if(line_counter_ == registers_[5]) {
line_is_visible_ = true;
line_counter_ = 0;
is_in_adjustment_period_ = false;
line_address_ = (registers_[12] << 8) | registers_[13];
bus_state_.refresh_address = line_address_;
}
} else {
// advance vertical counter
bus_state_.row_address++;
if(bus_state_.row_address == registers_[9]) {
line_address_ = bus_state_.refresh_address;
bus_state_.row_address = 0;
line_counter_++;
// check for end of visible lines
if(line_counter_ == registers_[6]) {
line_is_visible_ = false;
}
// check for start of vertical sync
if(line_counter_ == registers_[7]) {
bus_state_.vsync = true;
vsync_down_counter_ = 16; // TODO
}
// check for entry into the overflow area
if(line_counter_ == registers_[4]) {
is_in_adjustment_period_ = true;
bus_state_.row_address = 0;
line_counter_ = 0;
}
} else {
bus_state_.refresh_address = line_address_;
}
}
}
bus_state_.display_enable = line_is_visible_ && line_is_visible_;
bus_handler_.perform_bus_cycle(bus_state_);
}
}
@ -53,7 +127,6 @@ template <class T> class CRTC6845 {
void set_register(uint8_t value) {
registers_[selected_register_] = value;
if(!selected_register_) printf("Horizontal total: %d\n", value);
}
private:
@ -62,6 +135,16 @@ template <class T> class CRTC6845 {
uint8_t registers_[16];
int selected_register_;
uint8_t character_counter_;
uint8_t line_counter_;
bool character_is_visible_, line_is_visible_;
int hsync_down_counter_;
int vsync_down_counter_;
bool is_in_adjustment_period_;
uint16_t line_address_;
};
}