From f7887b745ed063f217c2946fd3ea11431daa8792 Mon Sep 17 00:00:00 2001
From: Colby <colby@taplaboratories.com.au>
Date: Thu, 21 Jul 2016 18:09:11 +1000
Subject: [PATCH] rewrote ROM controller

---
 lib/waterfoul/mbc/rom.rb | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/lib/waterfoul/mbc/rom.rb b/lib/waterfoul/mbc/rom.rb
index 71b9960..2484c69 100644
--- a/lib/waterfoul/mbc/rom.rb
+++ b/lib/waterfoul/mbc/rom.rb
@@ -1,29 +1,26 @@
 module Waterfoul
   module MBC
     class ROM
-      EXTERNAL_RAM_START_ADDR = 0xA000
+      EXTERNAL_RAM_SIZE = 0x1FFF
 
       def initialize(program)
-        @external_ram = []
+        @external_ram = Array.new EXTERNAL_RAM_SIZE, 0
         @program = program
       end
 
       def [](i)
-        case i & 0xE000
-        when 0xA000,0xB000
-          @external_ram[i]
+        case i
+        when 0xA000...0xC000
+          @external_ram[i - 0xA000]
         else
           @program[i]
         end
       end
 
       def []=(i,v)
-        case i & 0xE000
-        when 0xA000, 0xB000
-          addr = i - EXTERNAL_RAM_START_ADDR
-          @external_ram[addr] = v
-        else
-          fail 'forbidden write to rom'
+        case i
+        when 0xA000...0xC000
+          @external_ram[i - 0xA000] = v
         end
       end
     end