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Reguess state machine, fixing startup display.

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This commit is contained in:
Thomas Harte 2024-03-23 21:38:35 -04:00
parent 3cf262d1f7
commit 189dd176de
1 changed files with 47 additions and 40 deletions
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87
Machines/Acorn/Archimedes/Video.hpp
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@ -111,20 +111,11 @@ struct Video {
void tick() {
// Pick new horizontal state, possibly rolling over into the vertical.
horizontal_state_.increment_position();
horizontal_state_.phase =
horizontal_timing_.phase_after(
horizontal_state_.position,
horizontal_state_.phase);
horizontal_state_.increment_position(horizontal_timing_);
if(horizontal_state_.position == horizontal_timing_.period ) {
if(horizontal_state_.position == horizontal_timing_.period) {
horizontal_state_.position = 0;
vertical_state_.increment_position();
vertical_state_.phase =
vertical_timing_.phase_after(
vertical_state_.position,
vertical_state_.phase);
vertical_state_.increment_position(vertical_timing_);
if(vertical_state_.position == vertical_timing_.period) {
vertical_state_.position = 0;
@ -184,14 +175,14 @@ struct Video {
// Determine current output phase.
Phase new_phase;
switch(vertical_state_.phase) {
switch(vertical_state_.phase()) {
case Phase::Sync: new_phase = Phase::Sync; break;
case Phase::Blank: new_phase = Phase::Blank; break;
case Phase::Border:
new_phase = horizontal_state_.phase == Phase::Display ? Phase::Border : horizontal_state_.phase;
new_phase = horizontal_state_.phase() == Phase::Display ? Phase::Border : horizontal_state_.phase();
break;
case Phase::Display:
new_phase = horizontal_state_.phase;
new_phase = horizontal_state_.phase();
break;
}
@ -244,17 +235,56 @@ private:
const uint8_t *ram_ = nullptr;
Outputs::CRT::CRT crt_;
// Horizontal and vertical timing.
struct Timing {
uint32_t period = 0;
uint32_t sync_width = 0;
uint32_t border_start = 0;
uint32_t border_end = 0;
uint32_t display_start = 0;
uint32_t display_end = 0;
uint32_t cursor_start = 0;
uint32_t cursor_end = 0;
};
Timing horizontal_timing_, vertical_timing_;
// Current video state.
enum class Phase {
Sync, Blank, Border, Display,
};
struct State {
uint32_t position = 0;
Phase phase = Phase::Sync;
void increment_position() {
void increment_position(const Timing &timing) {
++position;
if(position == 1024) position = 0;
if(position == timing.period) {
sync_active = timing.sync_width;
display_started = !timing.display_start;
display_ended = !timing.display_end;
border_started = !timing.border_start;
border_ended = !timing.border_end;
} else {
sync_active &= position != timing.sync_width;
display_started |= position == timing.display_start;
display_ended |= position == timing.display_end;
border_started |= position == timing.border_start;
border_ended |= position == timing.border_end;
}
}
bool sync_active = true;
bool border_started = false;
bool border_ended = false;
bool display_started = false;
bool display_ended = false;
Phase phase() const {
if(sync_active) return Phase::Sync;
if(display_started && !display_ended) return Phase::Display;
if(border_started && !border_ended) return Phase::Border;
return Phase::Blank;
}
};
State horizontal_state_, vertical_state_;
@ -272,29 +302,6 @@ private:
// Ephemeral address state.
uint32_t address_ = 0;
// Horizontal and vertical timing.
struct Timing {
uint32_t period = 0;
uint32_t sync_width = 0;
uint32_t border_start = 0;
uint32_t border_end = 0;
uint32_t display_start = 0;
uint32_t display_end = 0;
uint32_t cursor_start = 0;
uint32_t cursor_end = 0;
Phase phase_after(uint32_t position, Phase current_phase) {
if(position == sync_width) return Phase::Blank;
if(position == border_start) return Phase::Border;
if(position == display_start) return Phase::Display;
if(position == display_end) return Phase::Border;
if(position == border_end) return Phase::Blank;
if(position == period) return Phase::Sync;
return current_phase;
}
};
Timing horizontal_timing_, vertical_timing_;
// Colour palette, converted to internal format.
uint16_t border_colour_;
std::array<uint16_t, 16> colours_{};