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Tidies code a little and thereby uncovers and corrects one cause of output instability.

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This commit is contained in:
Thomas Harte 2017-11-30 22:19:53 -05:00
parent 9c8158753e
commit edcbb3dfed
1 changed files with 45 additions and 19 deletions
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64
Components/9918/9918.cpp
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@ -85,8 +85,10 @@ void TMS9918::run_for(const HalfCycles cycles) {
int cycles_left = std::min(342 - column_, int_cycles);
column_ += cycles_left;
if(row_ < 192) {
// Do memory accesses.
if(row_ < 192 && !blank_screen_) {
// ------------------------
// Perform memory accesses.
// ------------------------
switch(line_mode_) {
case LineMode::Text:
while(access_pointer_ < (column_ >> 1)) {
@ -94,17 +96,20 @@ void TMS9918::run_for(const HalfCycles cycles) {
access_pointer_ = std::min(29, column_ >> 1);
}
if(access_pointer_ >= 29) {
int end = std::min(149, column_);
const int row_base = pattern_name_address_ + (row_ >> 3) * 40;
int character_column = (access_pointer_ - 29) / 3;
const int end = std::min(149, column_);
while(access_pointer_ < end) {
// Even worse than below; work to do.
int character_column = (access_pointer_ - 29) / 3;
switch(access_pointer_%3) {
case 2: pattern_name_ = ram_[row_base + character_column]; break;
case 1: break;
case 2:
pattern_name_ = ram_[row_base + character_column];
break;
case 1: break; // TODO: sprites / CPU access.
case 0:
colour_buffer_[character_column] = text_background_colour_;
pattern_buffer_[character_column] = ram_[pattern_generator_table_address_ + (pattern_name_ << 3) + (row_ & 7)];
character_column++;
break;
}
access_pointer_++;
@ -149,24 +154,43 @@ void TMS9918::run_for(const HalfCycles cycles) {
}
break;
}
// --------------------
// End memory accesses.
// --------------------
// Pixels.
// ----------------------
// Output horizontal sync
// ----------------------
if(!output_column_ && column_ >= 26) {
crt_->output_sync(static_cast<unsigned int>(26));
output_column_ = 26;
}
// TODO: colour burst.
// --------------------------
// TODO: output colour burst.
// --------------------------
// -------------------
// Output left border.
// -------------------
if(output_column_ >= 26) {
int pixels_end = std::min(first_pixel_column_, column_);
if(output_column_ < pixels_end) {
output_border(pixels_end - output_column_);
output_column_ = pixels_end;
// Grab a pointer for drawing pixels to, if the moment has arrived.
if(pixels_end == first_pixel_column_) {
pixel_target_ = reinterpret_cast<uint32_t *>(crt_->allocate_write_area(static_cast<unsigned int>(first_right_border_column_ - first_pixel_column_)));
}
}
}
// --------------
// Output pixels.
// --------------
if(output_column_ >= first_pixel_column_) {
int pixels_end = std::min(first_right_border_column_, column_);
@ -174,13 +198,11 @@ void TMS9918::run_for(const HalfCycles cycles) {
switch(line_mode_) {
case LineMode::Text:
while(output_column_ < pixels_end) {
int base = (output_column_ - first_pixel_column_);
int address = base / 6;
uint8_t colour = colour_buffer_[address];
uint8_t pattern = pattern_buffer_[address];
pattern >>= ((base % 6)^7);
const int base = (output_column_ - first_pixel_column_);
const int address = base / 6;
const uint8_t pattern = pattern_buffer_[address] << (base % 6);
*pixel_target_ = (pattern&1) ? palette[colour >> 4] : palette[colour & 15];
*pixel_target_ = (pattern&0x80) ? palette[text_colour_] : palette[background_colour_];
pixel_target_ ++;
output_column_ ++;
}
@ -206,7 +228,11 @@ void TMS9918::run_for(const HalfCycles cycles) {
crt_->output_data(static_cast<unsigned int>(first_right_border_column_ - first_pixel_column_), 1);
}
}
if(column_ >= first_pixel_column_) {
// --------------------
// Output right border.
// --------------------
if(output_column_ >= first_right_border_column_) {
output_border(column_ - output_column_);
output_column_ = column_;
}
@ -221,7 +247,7 @@ void TMS9918::run_for(const HalfCycles cycles) {
crt_->output_sync(static_cast<unsigned int>(26));
output_column_ = 26;
}
if(column_ >= 26) {
if(output_column_ >= 26) {
output_border(column_ - output_column_);
output_column_ = column_;
}
@ -287,7 +313,7 @@ void TMS9918::set_register(int address, uint8_t value) {
break;
case 1:
blank_screen_ = !!(low_write_ & 0x40);
blank_screen_ = !(low_write_ & 0x40);
generate_interrupts_ = !!(low_write_ & 0x20);
next_screen_mode_ = (screen_mode_ & 1) | ((low_write_ & 0x18) >> 3);
sprites_16x16_ = !!(low_write_ & 0x02);