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;