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gb6/src/dmg.c

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#include <stdio.h>
#include <string.h>
#include "cpu.h"
#include "rom.h"
#include "lcd.h"
#include "dmg.h"
#include "mbc.h"
#include "types.h"
#include "bootstrap.h"
void dmg_new(struct dmg *dmg, struct cpu *cpu, struct rom *rom, struct lcd *lcd)
{
dmg->cpu = cpu;
dmg->rom = rom;
dmg->lcd = lcd;
dmg->joypad = 0xf; // nothing pressed
dmg->action_buttons = 0xf;
}
void dmg_set_button(struct dmg *dmg, int field, int button, int pressed)
{
u8 *mod;
if (field == FIELD_JOY) {
mod = &dmg->joypad;
} else if (field == FIELD_ACTION) {
mod = &dmg->action_buttons;
} else {
printf("setting invalid button state\n");
return;
}
if (pressed) {
*mod &= ~button;
} else {
*mod |= button;
}
}
static u8 get_button_state(struct dmg *dmg)
{
u8 ret = 0xf0;
if (dmg->action_selected) {
ret |= dmg->action_buttons;
}
if (dmg->joypad_selected) {
ret |= dmg->joypad;
}
return ret;
}
u8 dmg_read(void *_dmg, u16 address)
{
struct dmg *dmg = (struct dmg *) _dmg;
u8 mbc_data;
if (mbc_read(dmg->rom->mbc, dmg, address, &mbc_data)) {
return mbc_data;
}
// if (address < 0x100) {
// return dmg_boot_rom[address];
// } else if (address < 0x4000) {
if (address < 0x4000) {
return dmg->rom->data[address];
} else if (address < 0x8000) {
return dmg->rom->data[address];
} else if (address < 0xa000) {
return dmg->video_ram[address - 0x8000];
} else if (address < 0xc000) {
printf("RAM bank not handled by MBC\n");
return 0xff;
} else if (address < 0xe000) {
return dmg->main_ram[address - 0xc000];
} else if (lcd_is_valid_addr(address)) {
return lcd_read(dmg->lcd, address);
} else if (address >= 0xff80 && address <= 0xfffe) {
return dmg->zero_page[address - 0xff80];
} else if (address == 0xff00) {
return get_button_state(dmg);
} else if (address == REG_TIMER_DIV) {
return (dmg->timer_div & 0xff00) >> 8;
} else if (address == REG_TIMER_COUNT) {
return dmg->timer_count;
} else if (address == REG_TIMER_MOD) {
return dmg->timer_mod;
} else if (address == REG_TIMER_CONTROL) {
return dmg->timer_control;
} else if (address == 0xff0f) {
return dmg->interrupt_requested;
} else if (address == 0xffff) {
return dmg->interrupt_enabled;
} else {
// not sure about any of this yet
// commented out bc of memory view window
// fprintf(stderr, "don't know how to read 0x%04x\n", address);
return 0xff;
}
}
void dmg_write(void *_dmg, u16 address, u8 data)
{
struct dmg *dmg = (struct dmg *) _dmg;
if (mbc_write(dmg->rom->mbc, dmg, address, data)) {
return;
}
if (address < 0x4000) {
printf("warning: writing 0x%04x in rom\n", address);
} else if (address < 0x8000) {
// TODO switchable rom bank
printf("warning: writing 0x%04x in rom\n", address);
} else if (address < 0xa000) {
dmg->video_ram[address - 0x8000] = data;
} else if (address < 0xc000) {
// TODO switchable ram bank
} else if (address < 0xe000) {
// printf("write ram %04x %02x\n", address, data);
dmg->main_ram[address - 0xc000] = data;
} else if (address == REG_TIMER_DIV) {
dmg->timer_div = 0;
} else if (address == REG_TIMER_COUNT) {
printf("write timer count\n");
dmg->timer_count = data;
} else if (address == REG_TIMER_MOD) {
printf("write timer mod\n");
dmg->timer_mod = data;
} else if (address == REG_TIMER_CONTROL) {
printf("write timer control\n");
dmg->timer_control = data;
} else if (address == 0xFF46) {
u16 src = data << 8;
int k = 0;
// printf("oam dma %04x\n", src);
for (u16 addr = src; addr < src + 0xa0; addr++) {
dmg->lcd->oam[k++] = dmg_read(dmg, addr);
}
} else if (lcd_is_valid_addr(address)) {
lcd_write(dmg->lcd, address, data);
} else if (address >= 0xff80 && address <= 0xfffe) {
dmg->zero_page[address - 0xff80] = data;
} else if (address == 0xff00) {
dmg->joypad_selected = !(data & (1 << 4));
dmg->action_selected = !(data & (1 << 5));
} else if (address == 0xff0f) {
dmg->interrupt_requested = data;
} else if (address == 0xffff) {
dmg->interrupt_enabled = data;
} else {
// not sure about any of this yet
}
}
void dmg_request_interrupt(struct dmg *dmg, int nr)
{
dmg->interrupt_requested |= nr;
}
// TODO move to lcd.c, it needs to be able to access dmg_read though
static void render_background(struct dmg *dmg, int lcdc, int is_window)
{
int bg_map = (lcdc & LCDC_BG_TILE_MAP) ? 0x9c00 : 0x9800;
int window_map = (lcdc & LCDC_WINDOW_TILE_MAP) ? 0x9c00 : 0x9800;
int map_base_addr = is_window ? window_map : bg_map;
int unsigned_mode = lcdc & LCDC_BG_TILE_DATA;
int tile_base_addr = unsigned_mode ? 0x8000 : 0x9000;
int palette = lcd_read(dmg->lcd, REG_BGP);
u8 *dest = is_window ? dmg->lcd->window : dmg->lcd->buf;
int tile_y, tile_x;
for (tile_y = 0; tile_y < 32; tile_y++) {
for (tile_x = 0; tile_x < 32; tile_x++) {
int eff_addr, b, i;
int off = 256 * 8 * tile_y + 8 * tile_x;
int tile_index = dmg_read(dmg, map_base_addr + (tile_y * 32 + tile_x));
if (unsigned_mode) {
eff_addr = tile_base_addr + 16 * tile_index;
} else {
eff_addr = tile_base_addr + 16 * (signed char) tile_index;
}
for (b = 0; b < 16; b += 2) {
int data1 = dmg_read(dmg, eff_addr + b);
int data2 = dmg_read(dmg, eff_addr + b + 1);
for (i = 7; i >= 0; i--) {
int col_index = (data1 & (1 << i)) ? 1 : 0;
col_index |= ((data2 & (1 << i)) ? 1 : 0) << 1;
dest[off] = (palette >> (col_index << 1)) & 3;
off++;
}
off += 248;
}
}
}
}
struct oam_entry {
u8 pos_y;
u8 pos_x;
u8 tile;
u8 attrs;
};
// TODO: only ten per scanline, priority, attributes, move to lcd.c
static void render_objs(struct dmg *dmg)
{
int k, lcd_x, lcd_y, off;
struct oam_entry *oam = (struct oam_entry *) dmg->lcd->oam;
int tall = lcd_isset(dmg->lcd, REG_LCDC, LCDC_OBJ_SIZE);
for (k = 0; k < 40; k++, oam++) {
if (oam->pos_y == 0 || oam->pos_y >= 160) {
continue;
}
if (oam->pos_x == 0 || oam->pos_x >= 168) {
continue;
}
int first_tile = 0x8000 + 16 * oam->tile;
int palette = oam->attrs & OAM_ATTR_PALETTE
? lcd_read(dmg->lcd, REG_OBP1)
: lcd_read(dmg->lcd, REG_OBP0);
lcd_x = oam->pos_x - 8;
lcd_y = oam->pos_y - 16;
off = 160 * lcd_y + lcd_x;
int b, i, tile_bytes = 16;
if (tall) {
tile_bytes = 32;
}
for (b = 0; b < tile_bytes; b += 2) {
int use_tile = b;
if (oam->attrs & OAM_ATTR_MIRROR_Y) {
use_tile = (tile_bytes - 2) - b;
}
int data1 = dmg_read(dmg, first_tile + use_tile);
int data2 = dmg_read(dmg, first_tile + use_tile + 1);
for (i = 7; i >= 0; i--) {
if (off < 0 || off >= 160 * 144) {
// terrible clipping. need to not have an if per-pixel
continue;
}
int use_index = i;
if (oam->attrs & OAM_ATTR_MIRROR_X) {
use_index = 7 - i;
}
int col_index = ((data1 & (1 << use_index)) ? 1 : 0)
| ((data2 & (1 << use_index)) ? 1 : 0) << 1;
if (col_index) {
dmg->lcd->pixels[off] = (palette >> (col_index << 1)) & 3;
}
off++;
}
off += 152;
}
}
}
static void timer_step(struct dmg *dmg)
{
dmg->timer_div++;
return;
if (!(dmg_read(dmg, REG_TIMER_CONTROL) & TIMER_CONTROL_ENABLED)) {
return;
}
int passed = dmg->cpu->cycle_count - dmg->last_timer_update;
u8 counter = dmg_read(dmg, REG_TIMER_COUNT);
u8 modulo = dmg_read(dmg, REG_TIMER_MOD);
counter++;
if (!counter) {
counter = modulo;
dmg_request_interrupt(dmg, INT_TIMER);
}
dmg_write(dmg, REG_TIMER_COUNT, counter);
dmg->last_timer_update = dmg->cpu->cycle_count;
}
void dmg_step(void *_dmg)
{
struct dmg *dmg = (struct dmg *) _dmg;
// order of dependencies? i think cpu needs to step first then update
// all other hw
cpu_step(dmg->cpu);
timer_step(dmg);
// each line takes 456 cycles
int cycle_diff = dmg->cpu->cycle_count - dmg->last_lcd_update;
if (cycle_diff >= 456) {
dmg->last_lcd_update = dmg->cpu->cycle_count;
int next_scanline = lcd_step(dmg->lcd);
// update LYC
if (next_scanline == lcd_read(dmg->lcd, REG_LYC)) {
lcd_set_bit(dmg->lcd, REG_STAT, STAT_FLAG_MATCH);
if (lcd_isset(dmg->lcd, REG_STAT, STAT_INTR_SOURCE_MATCH)) {
dmg_request_interrupt(dmg, INT_LCDSTAT);
}
} else {
lcd_clear_bit(dmg->lcd, REG_STAT, STAT_FLAG_MATCH);
}
if (next_scanline >= 144 && next_scanline < 154) {
lcd_set_mode(dmg->lcd, 1);
}
// TODO: do all of this per-scanline instead of everything in vblank
if (next_scanline == 144) {
// vblank has started, draw all the stuff from ram into the lcd
dmg_request_interrupt(dmg, INT_VBLANK);
if (lcd_isset(dmg->lcd, REG_STAT, STAT_INTR_SOURCE_VBLANK)) {
dmg_request_interrupt(dmg, INT_LCDSTAT);
}
int lcdc = lcd_read(dmg->lcd, REG_LCDC);
if (lcdc & LCDC_ENABLE_BG) {
render_background(dmg, lcdc, 0);
}
int window_enabled = lcdc & LCDC_ENABLE_WINDOW;
if (window_enabled) {
render_background(dmg, lcdc, 1);
}
lcd_apply_scroll(dmg->lcd, window_enabled);
if (lcdc & LCDC_ENABLE_OBJ) {
render_objs(dmg);
}
lcd_draw(dmg->lcd);
}
} else {
int scan = lcd_read(dmg->lcd, REG_LY);
if (scan < 144) {
if (cycle_diff < 80) {
lcd_set_mode(dmg->lcd, 2);
} else if (cycle_diff < 230) {
// just midpoint between 168 to 291, todo improve
lcd_set_mode(dmg->lcd, 3);
} else {
lcd_set_mode(dmg->lcd, 0);
}
} else {
// in vblank. mode should stay as 1
}
}
}
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