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Moves scrolling latch to proper position and implements 4-window fetching offset.

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This commit is contained in:
Thomas Harte 2018-10-11 22:36:27 -04:00
parent 6a94dda60d
commit f6af6778ab
2 changed files with 41 additions and 37 deletions
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14
Components/9918/9918.cpp
View File

@ -184,6 +184,17 @@ void TMS9918::run_for(const HalfCycles cycles) {
const int end_column = column_ + cycles_left;
// ---------------------------------------
// Latch scrolling position, if necessary.
// ---------------------------------------
if(column_ < 61 && end_column >= 61) {
if(!row_) {
master_system_.latched_vertical_scroll = master_system_.vertical_scroll;
}
master_system_.latched_horizontal_scroll = master_system_.horizontal_scroll;
}
// ------------------------
// Perform memory accesses.
// ------------------------
@ -313,7 +324,7 @@ void TMS9918::run_for(const HalfCycles cycles) {
// it is reloaded either when it overflows or upon every non-pixel line after the first.
// It is otherwise decremented.
if(is_sega_vdp(personality_)) {
if(row_ > 0 && row_ <= mode_timing_.pixel_lines+1) {
if(row_ >= mode_timing_.total_lines-1 && row_ <= mode_timing_.pixel_lines) {
--line_interrupt_counter;
if(line_interrupt_counter == 0xff) {
line_interrupt_pending_ = true;
@ -491,6 +502,7 @@ void TMS9918::set_register(int address, uint8_t value) {
case 8:
if(is_sega_vdp(personality_)) {
master_system_.horizontal_scroll = low_write_;
// printf("Set to %d at %d, %d\n", low_write_, row_, column_);
}
break;

64
Components/9918/Implementation/9918Base.hpp
View File

@ -334,6 +334,8 @@ class Base {
external_slots_16(n+16);
/*
TODO: explain offset by four windows in data gathering.
Fetching routines follow below; they obey the following rules:
1) input is a start position and an end position; they should perform the proper
@ -656,15 +658,6 @@ class Base {
slot(location+14): \
slot(location+15): fetch_tile(column+3)
// Latch scrolling position at slot 33 for now; unless or until
// a more accurate number becomes apparent.
if(start < 33 && end >= 33) {
if(!row_) {
master_system_.latched_vertical_scroll = master_system_.vertical_scroll;
}
master_system_.latched_horizontal_scroll = master_system_.horizontal_scroll;
}
// Determine the coarse horizontal scrolling offset; this isn't applied on the first two lines if the programmer has requested it.
const int horizontal_offset = (row_ >= 16 || !master_system_.horizontal_scroll_lock) ? (master_system_.latched_horizontal_scroll >> 3) : 0;
@ -689,39 +682,39 @@ class Base {
// ... and do the actual fetching, which follows this routine:
switch(start) {
default:
external_slots_4(0);
sprite_fetch_block(0, 0);
sprite_fetch_block(6, 2);
sprite_fetch_block(4, 0);
sprite_fetch_block(10, 2);
external_slots_4(12);
external_slot(16);
external_slots_4(16);
external_slot(20);
sprite_fetch_block(17, 4);
sprite_fetch_block(23, 6);
sprite_fetch_block(21, 4);
sprite_fetch_block(27, 6);
slot(33):
slot(29):
reset_sprite_collection();
do_external_slot();
external_slot(34);
external_slot(30);
sprite_y_read(35, 0);
sprite_y_read(36, 2);
sprite_y_read(37, 4);
sprite_y_read(38, 6);
sprite_y_read(39, 8);
sprite_y_read(40, 10);
sprite_y_read(41, 12);
sprite_y_read(42, 14);
sprite_y_read(31, 0);
sprite_y_read(32, 2);
sprite_y_read(33, 4);
sprite_y_read(34, 6);
sprite_y_read(35, 8);
sprite_y_read(36, 10);
sprite_y_read(37, 12);
sprite_y_read(38, 14);
background_fetch_block(43, 0, 16, scrolled_row_info);
background_fetch_block(59, 4, 22, scrolled_row_info);
background_fetch_block(75, 8, 28, scrolled_row_info);
background_fetch_block(91, 12, 34, scrolled_row_info);
background_fetch_block(107, 16, 40, scrolled_row_info);
background_fetch_block(123, 20, 46, scrolled_row_info);
background_fetch_block(139, 24, 52, row_info);
background_fetch_block(156, 28, 58, row_info);
background_fetch_block(39, 0, 16, scrolled_row_info);
background_fetch_block(55, 4, 22, scrolled_row_info);
background_fetch_block(71, 8, 28, scrolled_row_info);
background_fetch_block(87, 12, 34, scrolled_row_info);
background_fetch_block(103, 16, 40, scrolled_row_info);
background_fetch_block(119, 20, 46, scrolled_row_info);
background_fetch_block(135, 24, 52, row_info);
background_fetch_block(152, 28, 58, row_info);
external_slots_4(168);
return;
}
@ -741,7 +734,6 @@ class Base {
void draw_tms_character(int start, int end);
void draw_tms_text(int start, int end);
void draw_sms(int start, int end);
};
}