 
     //MARK: Helpers
     private var memoryBankAddress: UInt16 = 0
-    private var screenMemoryAddress: UInt16 = 0
     private var borderLeftComparisonValue: Int = 24
     private var borderRightComparisonValue: Int = 344
     private var borderTopComparisonValue: UInt16 = 51

            return me
        case 0x16:
            return (mcm ? 0x10 : 0) //TODO: missing bit registers
        case 0x19:
            //TEMP: force NTSC timing
            return 0x70

        case 0x16:
            mcm = byte & 0x10 != 0
        case 0x18:
            cb = (byte & 0x0E) >> 1
            vm = (byte & 0xF0) >> 4
        case 0x20:
            ec = byte & 0x0F
        case 0x21:
