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Attempts improvements to video fetch timing. Alas, a lot of guess work here.

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This commit is contained in:
Thomas Harte 2021-03-22 15:59:03 -04:00
parent bdb3bce8d6
commit a6b75b8637
1 changed files with 49 additions and 22 deletions
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71
Machines/Sinclair/ZXSpectrum/Video.hpp
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@ -52,6 +52,7 @@ template <VideoTiming timing> class Video {
int lines_per_frame;
int first_delay;
int contended_period;
int first_fetch;
int delays[16];
};
@ -61,6 +62,7 @@ template <VideoTiming timing> class Video {
.lines_per_frame = 311,
.first_delay = 14361 * 2,
.contended_period = (14490 - 14361) * 2,
.first_fetch = 14364 * 2, // TODO: find a source for this, a guess.
.delays = {
2, 1,
0, 0,
@ -78,7 +80,7 @@ template <VideoTiming timing> class Video {
public:
void run_for(HalfCycles duration) {
constexpr auto timings = get_timings();
constexpr int first_line = timings.first_delay / timings.cycles_per_line;
constexpr int first_line = timings.first_fetch / timings.cycles_per_line;
constexpr int sync_position = 166 * 2;
constexpr int sync_length = 17 * 2;
constexpr int burst_position = sync_position + 40;
@ -125,31 +127,56 @@ template <VideoTiming timing> class Video {
}
if(pixel_target_) {
const int start_column = offset >> 3;
const int end_column = (offset + pixel_duration) >> 3;
const int start_column = offset >> 4;
const int end_column = (offset + pixel_duration) >> 4;
for(int column = start_column; column < end_column; column++) {
const uint8_t attributes = memory_[attribute_address_];
constexpr uint8_t masks[] = {0, 0xff};
const uint8_t pixels = memory_[pixel_address_] ^ masks[flash_mask_ & (attributes >> 7)];
const uint8_t colours[2] = {
palette[(attributes & 0x78) >> 3],
palette[((attributes & 0x40) >> 3) | (attributes & 0x07)],
const uint8_t attributes[2] = {
memory_[attribute_address_],
memory_[attribute_address_+1],
};
pixel_target_[0] = colours[(pixels >> 7) & 1];
pixel_target_[1] = colours[(pixels >> 6) & 1];
pixel_target_[2] = colours[(pixels >> 5) & 1];
pixel_target_[3] = colours[(pixels >> 4) & 1];
pixel_target_[4] = colours[(pixels >> 3) & 1];
pixel_target_[5] = colours[(pixels >> 2) & 1];
pixel_target_[6] = colours[(pixels >> 1) & 1];
pixel_target_[7] = colours[(pixels >> 0) & 1];
pixel_target_ += 8;
constexpr uint8_t masks[] = {0, 0xff};
const uint8_t pixels[2] = {
uint8_t(memory_[pixel_address_] ^ masks[flash_mask_ & (attributes[0] >> 7)]),
uint8_t(memory_[pixel_address_+1] ^ masks[flash_mask_ & (attributes[1] >> 7)]),
};
++pixel_address_;
++attribute_address_;
{
const uint8_t colours[2] = {
palette[(attributes[0] & 0x78) >> 3],
palette[((attributes[0] & 0x40) >> 3) | (attributes[0] & 0x07)],
};
pixel_target_[0] = colours[(pixels[0] >> 7) & 1];
pixel_target_[1] = colours[(pixels[0] >> 6) & 1];
pixel_target_[2] = colours[(pixels[0] >> 5) & 1];
pixel_target_[3] = colours[(pixels[0] >> 4) & 1];
pixel_target_[4] = colours[(pixels[0] >> 3) & 1];
pixel_target_[5] = colours[(pixels[0] >> 2) & 1];
pixel_target_[6] = colours[(pixels[0] >> 1) & 1];
pixel_target_[7] = colours[(pixels[0] >> 0) & 1];
pixel_target_ += 8;
}
{
const uint8_t colours[2] = {
palette[(attributes[1] & 0x78) >> 3],
palette[((attributes[1] & 0x40) >> 3) | (attributes[1] & 0x07)],
};
pixel_target_[0] = colours[(pixels[1] >> 7) & 1];
pixel_target_[1] = colours[(pixels[1] >> 6) & 1];
pixel_target_[2] = colours[(pixels[1] >> 5) & 1];
pixel_target_[3] = colours[(pixels[1] >> 4) & 1];
pixel_target_[4] = colours[(pixels[1] >> 3) & 1];
pixel_target_[5] = colours[(pixels[1] >> 2) & 1];
pixel_target_[6] = colours[(pixels[1] >> 1) & 1];
pixel_target_[7] = colours[(pixels[1] >> 0) & 1];
pixel_target_ += 8;
}
pixel_address_ += 2;
attribute_address_ += 2;
}
}