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Makes an attempt to provide the necessary hook for floating bus behaviour.

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This commit is contained in:
Thomas Harte 2021-03-22 22:34:28 -04:00
parent 19cd6a55d3
commit 60e77785e8
1 changed files with 50 additions and 45 deletions
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95
Machines/Sinclair/ZXSpectrum/Video.hpp
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@ -158,53 +158,40 @@ template <VideoTiming timing> class Video {
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[2] = {
memory_[attribute_address_],
memory_[attribute_address_+1],
};
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)]),
};
{
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;
}
last_fetches_[0] = memory_[pixel_address_];
last_fetches_[1] = memory_[attribute_address_];
last_fetches_[2] = memory_[pixel_address_+1];
last_fetches_[3] = memory_[attribute_address_+1];
pixel_address_ += 2;
attribute_address_ += 2;
constexpr uint8_t masks[] = {0, 0xff};
#define Output(n) \
{ \
const uint8_t pixels = \
uint8_t(last_fetches_[n] ^ masks[flash_mask_ & (last_fetches_[n+1] >> 7)]); \
\
const uint8_t colours[2] = { \
palette[(last_fetches_[n+1] & 0x78) >> 3], \
palette[((last_fetches_[n+1] & 0x40) >> 3) | (last_fetches_[n+1] & 0x07)], \
}; \
\
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; \
}
Output(0);
Output(2);
#undef Output
}
}
@ -322,6 +309,22 @@ template <VideoTiming timing> class Video {
return timings.delays[time_into_line & 15];
}
/*!
@returns Whatever the ULA or gate array has fetched this cycle, or 0xff if it has fetched nothing.
*/
uint8_t get_current_fetch() const {
constexpr auto timings = get_timings();
const int line = time_into_frame_ / timings.cycles_per_line;
if(line >= 192) return 0xff;
const int time_into_line = time_into_frame_ % timings.cycles_per_line;
if(time_into_line >= 256 || (time_into_line&4)) {
return 0xff;
}
return last_fetches_[time_into_line & 3];
}
/*!
Sets the current border colour.
*/
@ -358,6 +361,8 @@ template <VideoTiming timing> class Video {
int flash_counter_ = 0;
bool is_alternate_line_ = false;
uint8_t last_fetches_[4] = {0xff, 0xff, 0xff, 0xff};
#define RGB(r, g, b) (r << 4) | (g << 2) | b
static constexpr uint8_t palette[] = {
RGB(0, 0, 0), RGB(0, 0, 2), RGB(2, 0, 0), RGB(2, 0, 2),