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Added some additional documentation, started making steps towards returning sprites, fixed a counter bug that would exhibit as incorrect sync.

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This commit is contained in:
Thomas Harte 2017-01-31 20:30:32 -05:00
parent abe04334c2
commit f2437cb257
2 changed files with 18 additions and 16 deletions
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16
Machines/Atari2600/TIA.cpp
View File

@ -205,7 +205,7 @@ void TIA::set_player_delay(int player, bool delay)
void TIA::set_player_position(int player)
{
// TODO
player_[player].position = ((horizontal_counter_ - 68) + 6)%160;
}
void TIA::set_player_motion(int player, uint8_t motion)
@ -267,15 +267,6 @@ void TIA::clear_collision_flags()
{
}
// case 0: case 1: case 2: case 3: state = OutputState::Blank; break;
// case 4: case 5: case 6: case 7: state = OutputState::Sync; break;
// case 8: case 9: case 10: case 11: state = OutputState::ColourBurst; break;
// case 12: case 13: case 14:
// case 15: case 16: state = OutputState::Blank; break;
//
// case 17: case 18: state = vbextend ? OutputState::Blank : OutputState::Pixel; break;
// default: state = OutputState::Pixel; break;
void TIA::output_for_cycles(int number_of_cycles)
{
/*
@ -284,7 +275,7 @@ void TIA::output_for_cycles(int number_of_cycles)
NTSC colour clock.
Therefore, each line is composed of:
16 cycles: blank ; -> 16
16 cycles: sync ; -> 32
16 cycles: colour burst ; -> 48
@ -301,7 +292,7 @@ void TIA::output_for_cycles(int number_of_cycles)
if(horizontal_counter_ <= target) \
{ \
crt_->function((unsigned int)((horizontal_counter_ - output_cursor) * 2)); \
output_cursor = horizontal_counter_; \
horizontal_counter_ %= cycles_per_line; \
return; \
} \
else \
@ -337,7 +328,6 @@ void TIA::output_for_cycles(int number_of_cycles)
}
int duration = std::min(228, horizontal_counter_) - output_cursor;
crt_->output_blank((unsigned int)(duration * 2));
output_cursor += duration;
}
else
{

18
Machines/Atari2600/TIA.hpp
View File

@ -68,8 +68,12 @@ class TIA {
std::shared_ptr<Outputs::CRT::CRT> crt_;
// drawing methods
void output_for_cycles(int number_of_cycles);
void output_line();
inline void output_for_cycles(int number_of_cycles);
inline void output_line();
inline void draw_background(uint8_t *target, int start, int length);
inline void draw_playfield(uint8_t *target, int start, int length);
inline void draw_background_and_playfield(uint8_t *target, int start, int length);
// the master counter; counts from 0 to 228 with all visible pixels being in the final 160
int horizontal_counter_;
@ -84,8 +88,14 @@ class TIA {
// playfield state
uint8_t playfield_ball_colour_;
uint8_t background_colour_;
uint32_t background_[2];
int background_half_mask_;
uint32_t background_[2]; // contains two 20-bit bitfields representing the background state;
// at index 0 is the left-hand side of the playfield with bit 0 being
// the first bit to display, bit 1 the second, etc. Index 1 contains
// a mirror image of index 0. If the playfield is being displayed in
// mirroring mode, background_[0] will be output on the left and
// background_[1] on the right; otherwise background_[0] will be
// output twice.
// player state
struct Player {
@ -95,6 +105,8 @@ class TIA {
uint8_t colour; // the player colour
int reverse_mask; // 7 for a reflected player, 0 for normal
uint8_t motion; // low four bits used
uint8_t position; // in the range [0, 160) to indicate offset from the left margin, i.e. phase difference
// between the player counter and the background pixel counter.
} player_[2];
// missile state