各种使用单片机应用电路汇集，包括复位电路与晶振电路、低位地址锁存、外扩存储器及片选信号、RS_232串口通信电平转换-Brings together a variety of use MCU application circuit, including the reset circuit, crystal oscillator circuit, the low-order address latch, external expansion memory and chip-select signa