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OAM search and OAM timing in mode 3

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This commit is contained in:
Lior Halphon 2018-03-04 22:21:56 +02:00
parent 476133abd0
commit 3d1c8b50c4
2 changed files with 81 additions and 20 deletions
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98
Core/display.c
View File

@ -6,7 +6,7 @@
/* FIFO functions */
static inline unsigned fifo_size(GB_fifo_t *fifo)
static inline unsigned __attribute__((unused)) fifo_size(GB_fifo_t *fifo)
{
return (fifo->write_end - fifo->read_end) & 0xF;
}
@ -66,7 +66,7 @@ typedef struct __attribute__((packed)) {
uint8_t x;
uint8_t tile;
uint8_t flags;
} GB_sprite_t;
} GB_object_t;
static bool window_enabled(GB_gameboy_t *gb)
{
@ -97,7 +97,7 @@ static uint32_t __attribute__((unused)) get_pixel(GB_gameboy_t *gb, uint8_t x, u
uint8_t sprite_palette = 0;
uint16_t tile_address = 0;
uint8_t background_pixel = 0, sprite_pixel = 0;
GB_sprite_t *sprite = (GB_sprite_t *) &gb->oam;
GB_object_t *sprite = (GB_object_t *) &gb->oam;
uint8_t sprites_in_line = 0;
bool lcd_8_16_mode = (gb->io_registers[GB_IO_LCDC] & 4) != 0;
bool sprites_enabled = (gb->io_registers[GB_IO_LCDC] & 2) != 0;
@ -407,6 +407,40 @@ void GB_lcd_off(GB_gameboy_t *gb)
gb->ly_for_comparison = 0;
}
static void search_oam(GB_gameboy_t *gb)
{
/*
We have very little means to test how the OAM search timing actually
works so we currently implement it atomically.
This is enough for most cases except (All are TODOs):
- The OAM bug on the DMG (Not emulated at all)
- Changing object height via LCDC during mode 2
- What about changing during mode 3?
- Enabling and disabling sprites during mode 2
- Does this flag actually do anything in mode 2? Or only during mode 3?
*/
/* This reverse sorts the visible objects by location and priority */
GB_object_t *objects = (GB_object_t *) &gb->oam;
bool height_16 = (gb->io_registers[GB_IO_LCDC] & 4) != 0;
gb->n_visible_objs = 0;
for (uint8_t i = 0; i < 40; i++) {
signed y = objects[i].y - 16;
if (y <= gb->current_line && y + (height_16? 16 : 8) > gb->current_line) {
unsigned j = 0;
for (; j < gb->n_visible_objs; j++) {
if (objects[gb->visible_objs[j]].x <= objects[i].x) break;
}
memmove(gb->visible_objs + j + 1, gb->visible_objs + j, gb->n_visible_objs - j);
gb->visible_objs[j] = i;
gb->n_visible_objs++;
if (gb->n_visible_objs == 10) return;
}
}
}
static void render_pixel_if_possible(GB_gameboy_t *gb)
{
GB_fifo_item_t *fifo_item = NULL;
@ -444,8 +478,10 @@ static void render_pixel_if_possible(GB_gameboy_t *gb)
}
gb->position_in_line++;
}
void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
{
GB_object_t *objects = (GB_object_t *) &gb->oam;
GB_STATE_MACHINE(gb, display, cycles, 2) {
GB_STATE(gb, display, 1);
@ -465,9 +501,10 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
GB_STATE(gb, display, 15);
GB_STATE(gb, display, 16);
GB_STATE(gb, display, 17);
GB_STATE(gb, display, 19);
GB_STATE(gb, display, 20);
GB_STATE(gb, display, 21);
GB_STATE(gb, display, 22);
}
if (!(gb->io_registers[GB_IO_LCDC] & 0x80)) {
@ -529,6 +566,7 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
gb->io_registers[GB_IO_STAT] |= 2;
GB_STAT_update(gb);
gb->io_registers[GB_IO_STAT] &= ~3;
search_oam(gb);
}
GB_SLEEP(gb, display, 7, 1);
@ -556,8 +594,8 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
gb->position_in_line = - (gb->io_registers[GB_IO_SCX] & 7) - 8;
gb->fetcher_x = ((gb->io_registers[GB_IO_SCX]) / 8) & 0x1f;
gb->cycles_for_line += 6;
GB_SLEEP(gb, display, 10, 6);
gb->cycles_for_line += 5;
GB_SLEEP(gb, display, 10, 5);
/* The actual rendering cycle */
gb->fetcher_divisor = false;
@ -565,6 +603,26 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
gb->fifo_paused = true;
gb->in_window = false;
while (true) {
/* Handle objects */
while (gb->n_visible_objs != 0 &&
(gb->io_registers[GB_IO_LCDC] & 2) != 0 &&
objects[gb->visible_objs[gb->n_visible_objs - 1]].x == (uint8_t)(gb->position_in_line + 8)) {
if (!gb->fetching_objects) {
/* Penalty for interrupting the fetcher */
uint8_t penalty = (uint8_t[]){5, 4, 3, 2, 1, 0, 0, 0}[gb->fetcher_state * 2 + gb->fetcher_divisor];
gb->cycles_for_line += penalty;
GB_SLEEP(gb, display, 19, penalty);
}
gb->fetching_objects = true;
gb->cycles_for_line += 6;
GB_SLEEP(gb, display, 20, 6);
gb->n_visible_objs--;
}
gb->fetching_objects = false;
/* Handle window */
/* Todo: Timing not verified by test ROM */
if (!gb->in_window && window_enabled(gb) &&
@ -628,20 +686,20 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
gb->fifo_paused = false;
}
if (gb->position_in_line == 160) break;
else if (gb->position_in_line == 159) {
gb->io_registers[GB_IO_STAT] &= ~3;
gb->oam_read_blocked = false;
gb->vram_read_blocked = false;
gb->oam_write_blocked = false;
gb->vram_write_blocked = false;
if (gb->hdma_on_hblank) {
gb->hdma_on = true;
gb->hdma_cycles = 0;
}
}
gb->cycles_for_line++;
GB_SLEEP(gb, display, 20, 1);
GB_SLEEP(gb, display, 21, 1);
}
gb->io_registers[GB_IO_STAT] &= ~3;
gb->oam_read_blocked = false;
gb->vram_read_blocked = false;
gb->oam_write_blocked = false;
gb->vram_write_blocked = false;
if (gb->hdma_on_hblank) {
gb->hdma_on = true;
gb->hdma_cycles = 0;
}
gb->cycles_for_line++;
GB_SLEEP(gb, display, 22, 1);
GB_STAT_update(gb);
GB_SLEEP(gb, display, 11, LINE_LENGTH - gb->cycles_for_line);
}
@ -836,7 +894,7 @@ uint8_t GB_get_oam_info(GB_gameboy_t *gb, GB_oam_info_t *dest, uint8_t *sprite_h
*sprite_height = (gb->io_registers[GB_IO_LCDC] & 4) ? 16:8;
uint8_t oam_to_dest_index[40] = {0,};
for (unsigned y = 0; y < LINES; y++) {
GB_sprite_t *sprite = (GB_sprite_t *) &gb->oam;
GB_object_t *sprite = (GB_object_t *) &gb->oam;
uint8_t sprites_in_line = 0;
for (uint8_t i = 0; i < 40; i++, sprite++) {
int sprite_y = sprite->y - 16;

3
Core/gb.h
View File

@ -421,6 +421,9 @@ struct GB_gameboy_internal_s {
bool fetcher_divisor; // The fetcher runs at 2MHz
bool fifo_paused;
bool in_window;
uint8_t visible_objs[10];
uint8_t n_visible_objs;
bool fetching_objects;
);
/* Unsaved data. This includes all pointers, as well as everything that shouldn't be on a save state */