From 131685b8648be1b13102a1562eafd1cc23fadee4 Mon Sep 17 00:00:00 2001
From: Thomas <thomas@thomasw.dev>
Date: Sat, 9 Dec 2023 21:36:46 +0100
Subject: [PATCH] Fix: OAMADDx address is a word address, not a byte address

---
 src/snes/ppu/bus.rs   |  8 ++++----
 src/snes/ppu/tests.rs | 15 ++++++++-------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/src/snes/ppu/bus.rs b/src/snes/ppu/bus.rs
index de56b4f..9c3c616 100644
--- a/src/snes/ppu/bus.rs
+++ b/src/snes/ppu/bus.rs
@@ -141,18 +141,18 @@ where
                 0x2101 => Some(self.obsel = val),
                 // OAMADDL - OAM Address and Priority Rotation (W)
                 0x2102 => {
-                    let v = self.oamadd.get() & 0xFF00;
-                    Some(self.oamadd.set(v | val as u16))
+                    let v = (self.oamadd.get() >> 1) & 0xFF00;
+                    Some(self.oamadd.set((v | val as u16) << 1))
                 }
                 // OAMADDH - OAM Address and Priority Rotation (W)
                 0x2103 => {
-                    let v = self.oamadd.get() & 0x00FF;
+                    let v = (self.oamadd.get() >> 1) & 0x00FF;
                     let val = val & 0x83; // bit 10-14 unused
                     if val & 0x80 != 0 {
                         // Obj priority
                         // TODO
                     }
-                    Some(self.oamadd.set(v | (val as u16) << 8))
+                    Some(self.oamadd.set((v | (val as u16) << 8) << 1))
                 }
                 // OAMDATA - OAM Data Write (W)
                 0x2104 => {
diff --git a/src/snes/ppu/tests.rs b/src/snes/ppu/tests.rs
index 5e96b51..cf27af2 100644
--- a/src/snes/ppu/tests.rs
+++ b/src/snes/ppu/tests.rs
@@ -201,8 +201,8 @@ fn oam_write_seq() {
     assert_eq!(p.oam[0..5], [0xAA, 0xBB, 0xCC, 0xDD, 0]);
 
     // Test end of OAM towards the 32 byte extension table
-    p.write(0x2102, (510 & 0xFF) as u8);
-    p.write(0x2103, (510 >> 8) as u8);
+    p.write(0x2102, ((510 >> 1) & 0xFF) as u8);
+    p.write(0x2103, ((510 >> 1) >> 8) as u8);
     assert_eq!(p.oam[510..513], [0, 0, 0]);
     p.write(0x2104, 0xAA);
     assert_eq!(p.oam[510..513], [0, 0, 0]);
@@ -216,8 +216,8 @@ fn oam_write_seq() {
 fn oam_write_exttable() {
     let mut p = ppu();
     assert_eq!(p.oam[512], 0);
-    p.write(0x2102, (512 & 0xFF) as u8);
-    p.write(0x2103, (512 >> 8) as u8);
+    p.write(0x2102, ((512 >> 1) & 0xFF) as u8);
+    p.write(0x2103, ((512 >> 1) >> 8) as u8);
     p.write(0x2104, 0xAA);
     assert_eq!(p.oam[512], 0xAA);
 }
@@ -226,8 +226,8 @@ fn oam_write_exttable() {
 fn oam_write_exttable_mirror() {
     let mut p = ppu();
     assert_eq!(p.oam[512], 0);
-    p.write(0x2102, (0x220 & 0xFF) as u8);
-    p.write(0x2103, (0x220 >> 8) as u8);
+    p.write(0x2102, (0x120 & 0xFF) as u8);
+    p.write(0x2103, (0x120 >> 8) as u8);
     p.write(0x2104, 0xAA);
     assert_eq!(p.oam[512], 0xAA);
 }
@@ -250,8 +250,9 @@ fn oam_read() {
     p.oam[3] = 1;
     p.oam[4] = 2;
     p.oam[5] = 3;
-    p.write(0x2102, 3);
+    p.write(0x2102, 3 >> 1);
     p.write(0x2103, 0);
+    assert_eq!(p.read(0x2138), Some(0));
     assert_eq!(p.read(0x2138), Some(1));
     assert_eq!(p.read(0x2138), Some(2));
     assert_eq!(p.read(0x2138), Some(3));