The extension of the microprocessor memory , the keyboard and display adopt typical circuits . because this system have to expend a lot of memory , i / o are used masterly in order to satisfy the design demand 單片機系統外圍的的存儲器擴展、鍵盤和顯示等部分以選取經典電路為主要設計思路,但本系統要擴展海量存儲器,所以巧妙的使用和分配了i o口,以滿足設計要求。