start working on ppu

2 files changed, 39 insertions, 0 deletions

diff --git a/ppu.c b/ppu.c
index 4ae0162..5dc20a3 100644
--- a/ppu.c
+++ b/ppu.c
@@ -13,3 +13,16 @@ ppu_tick(void)
         if (ppu.scanlines >= 262)
                 ppu.scanlines -= 262;
 }
+
+uint8_t
+ppu_read(uint16_t addr)
+{
+}
+
+void
+ppu_write(uint16_t addr, uint8_t byte)
+{
+        static uint8_t prev;
+
+        prev = byte;
+}
diff --git a/ppu.h b/ppu.h
index 6bc8b5a..ffd66d7 100644
--- a/ppu.h
+++ b/ppu.h
@@ -12,6 +12,32 @@ struct ppu {
         uint8_t palette[16*2];
         uint16_t cycles, scanlines;
         struct rom *rom;
+
+        struct ppu_ctrl {       /* $2000 */
+                uint8_t nmi_enable : 1;
+                uint8_t master_slave : 1;
+                uint8_t sprite_height : 1;
+                uint8_t bg_tile_sel : 1;
+                uint8_t sprite_tile_sel : 1;
+                uint8_t inc_mode : 1;
+                uint8_t nametable_sel : 2;
+        } ctrl;
+        struct ppu_mask {       /* $2001 */
+                uint8_t colour_emphasis : 3;
+                uint8_t sprite_enable : 1;
+                uint8_t bg_enable : 1;
+                uint8_t sprite_left_enable : 1;
+                uint8_t bg_left_enable : 1;
+                uint8_t grayscale : 1;
+        } mask;
+        struct ppu_status {     /* $2002 */
+                uint8_t vblank : 1;
+                uint8_t sprite0_hit : 1;
+                uint8_t sprite_overflow : 1;
+                uint8_t pad : 5;
+        } status;
+        uint8_t oam_addr;       /* $2003 */
+        uint8_t oam_data;       /* $2004 */
 };
 extern struct ppu ppu;