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Implements every-other-cycle-during-pixels RAM timing.

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This commit is contained in:
Thomas Harte 2019-09-21 17:25:20 -04:00
parent e760421f6f
commit e7bf0799b6
3 changed files with 18 additions and 19 deletions
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12
Machines/Apple/Macintosh/Macintosh.cpp
View File

@ -337,12 +337,12 @@ template <Analyser::Static::Macintosh::Target::Model model> class ConcreteMachin
memory_base = ram_.data();
word_address &= ram_mask_;
// Apply a delay due to video contention if applicable; technically this is
// incorrectly placed — strictly speaking here I'm extending the part of the
// bus cycle after DTACK rather than delaying DTACK. But it adds up to the
// same thing.
if(ram_subcycle_ < 4) {
delay = HalfCycles(4 - ram_subcycle_);
// Apply a delay due to video contention if applicable; scheme applied:
// only every other access slot is available during the period of video
// output. I believe this to be correct for the 128k, 512k and Plus.
// More research to do on other models.
if(video_is_outputting() && ram_subcycle_ < 8) {
delay = HalfCycles(8 - ram_subcycle_);
advance_time(delay);
}
} break;

12
Machines/Apple/Macintosh/Video.cpp
View File

@ -14,11 +14,6 @@ using namespace Apple::Macintosh;
namespace {
const HalfCycles line_length(704);
const int number_of_lines = 370;
const HalfCycles frame_length(line_length * HalfCycles(number_of_lines));
const int sync_start = 36;
const int sync_end = 38;
}
@ -183,13 +178,6 @@ HalfCycles Video::get_next_sequence_point() {
}
}
bool Video::is_outputting(HalfCycles offset) {
const auto offset_position = frame_position_ + offset % frame_length;
const int column = (offset_position % line_length).as_int() >> 4;
const int line = (offset_position / line_length).as_int();
return line < 342 && column < 32;
}
void Video::set_use_alternate_buffers(bool use_alternate_screen_buffer, bool use_alternate_audio_buffer) {
use_alternate_screen_buffer_ = use_alternate_screen_buffer;
use_alternate_audio_buffer_ = use_alternate_audio_buffer;

13
Machines/Apple/Macintosh/Video.hpp
View File

@ -17,6 +17,12 @@
namespace Apple {
namespace Macintosh {
static const HalfCycles line_length(704);
static const int number_of_lines = 370;
static const HalfCycles frame_length(line_length * HalfCycles(number_of_lines));
static const int sync_start = 36;
static const int sync_end = 38;
/*!
Models the 68000-era Macintosh video hardware, producing a 512x348 pixel image,
within a total scanning area of 370 lines, at 352 cycles per line.
@ -61,7 +67,12 @@ class Video {
@returns @c true if in @c offset half cycles from now, the video will be outputting pixels;
@c false otherwise.
*/
bool is_outputting(HalfCycles offset = HalfCycles(0));
bool is_outputting(HalfCycles offset = HalfCycles(0)) {
const auto offset_position = frame_position_ + offset % frame_length;
const int column = (offset_position % line_length).as_int() >> 4;
const int line = (offset_position / line_length).as_int();
return line < 342 && column < 32;
}
/*!
@returns the amount of time until there is next a transition on the