Fixed a couple bugs. Removed mmSwitchRegister(). Added switchBank()

src/memory/mmc.js

   }
 
   addMemModule(mem){
-    if (!(mem instanceof Memory))
-      throw new ValueError("Only Memory instances can be added to MMC Banks.");
+    if (!(mem instanceof IMem))
+      throw new ValueError("Only IMem instances can be added to MMC Banks.");
     if (this.__mem.length >= 4)
       throw new RangeError("Bank handling maximum memory modules.");
     if (this.__mem.length > 0 && mem.size !== this.__mem[0].size)
     if (addroff < 0 || addroff === this.size){
       this.__switches.push(new Switch(mem));
     } else {
-      offset = 0;
+      let offset = 0;
       for (let s=0; s < this.__switches.length; s++){
         if (addroff === offset){
           if (this.__switches[s].mem.size !== mem.size)
     }
     return this;
   }
-  
-  mmSwitchRegister(){
-    return (function(byte){
-      let mmcidx = (byte & 0xF0) >> 4;
-      if (mmcidx < this.__switches.length){
-        this.__switches[mmcidx].idx = (byte & 0x0F);
-      }
-    }).bind(this);
-  }
+
+  switchBank(bank){
+    // The variable <bank> contains two 4 bit offsets.
+    // The upper 4 bits is the bank switch offset.
+    // The lower 4 bits is the bank offset within the switch.
+    let mmcidx = (bank & 0xF0) >> 4;
+    if (mmcidx < this.__switches.length){
+      this.__switches[mmcidx].idx = (bank & 0x0F);
+    }
+  } 
 }
 
 module.exports = MMC;