From 502df9b6342082fb04894ce85810295528f92e34 Mon Sep 17 00:00:00 2001
From: Matthew Berry <me@mattrb.com>
Date: Sat, 7 Nov 2020 19:40:29 -0800
Subject: [PATCH] cartridge oob data, wait states 1/2

---
 src/crab/bus.cr       | 14 ++++++++------
 src/crab/cartridge.cr | 14 ++++++--------
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/src/crab/bus.cr b/src/crab/bus.cr
index 152e1e2..3528d8d 100644
--- a/src/crab/bus.cr
+++ b/src/crab/bus.cr
@@ -19,9 +19,11 @@ class Bus
       address = 0x1FFFF_u32 & index
       address -= 0x8000 if address > 0x17FFF
       @gba.ppu.vram[address]
-    when 0x7      then @gba.ppu.oam[index & 0x3FF]
-    when 0x8, 0x9 then @gba.cartridge[index & 0x7FFFFFF]
-    else               raise "Unmapped read: #{hex_str index.to_u32}"
+    when 0x7 then @gba.ppu.oam[index & 0x3FF]
+    when 0x8, 0x9,
+         0xA, 0xB,
+         0xC, 0xD then @gba.cartridge[index & 0x01FFFFFF]
+    else raise "Unmapped read: #{hex_str index.to_u32}"
     end
   end
 
@@ -73,9 +75,9 @@ class Bus
       address = 0x1FFFF_u32 & index
       address -= 0x8000 if address > 0x17FFF
       @gba.ppu.vram[address] = value
-    when 0x7      then @gba.ppu.oam[index & 0x3FF]
-    when 0x8, 0x9 then @gba.cartridge[index & 0x7FFFFFF] = value
-    else               raise "Unmapped write: #{hex_str index.to_u32}"
+    when 0x7 then @gba.ppu.oam[index & 0x3FF]
+    when 0x8, 0x9 # can't write to cartridge
+    else raise "Unmapped write: #{hex_str index.to_u32}"
     end
   end
 
diff --git a/src/crab/cartridge.cr b/src/crab/cartridge.cr
index 4471807..5437b9d 100644
--- a/src/crab/cartridge.cr
+++ b/src/crab/cartridge.cr
@@ -7,18 +7,16 @@ class Cartridge
     io.to_s
   }
 
+  @rom = Bytes.new 0x02000000 do |addr|
+    oob = 0xFFFF & (addr >> 1)
+    (oob >> (8 * (addr & 1))).to_u8!
+  end
+
   def initialize(rom_path : String)
-    @rom = File.open rom_path do |file|
-      bytes = Bytes.new file.size
-      file.read bytes
-      bytes
-    end
+    File.open(rom_path) { |file| file.read @rom }
   end
 
   def [](index : Int) : Byte
     @rom[index]
   end
-
-  def []=(index : Int, value : Byte) : Nil
-  end
 end