AT89C2051只有15个IO口，要显示8位数码管有点吃力，必需扩展，所以找来74HC595串转并移位寄存器，一个做段显一个做位选，只用三个IO口就解决了8+8的显示，如果要再多一点也不怕，不过2051只有2K的存贮空间，也限制了显示位数。DS1302占用3个IO，这样一个P1只用了6个IO，还有两个空着，准备设置一个LED感应自动开关和一个DS18B20，如果程序大小允许再加入红外摇控，把LED显示做大一点，就是一款实用的电子钟。-AT89C2051 only then 15 IO mouths, must demonstrate that 8 nixietubes are a little strenuous, essential expansion, therefore looks for the 74HC595 string to transfer and the shift register, makes section obviously one to make the position to elect, only used three IO mouths to solve 8+8 demonstrations, if must many not fear again, but 2051 only then 2K storage space, also has limited the demonstration figure. DS1302 takes 3 IO, this kind of P1 has only used 6 IO, but also two are emptying, prepares to establish LED to induce the autoswitch and DS18B20, if the procedure size permission joins again infrared swings controls, does big some LED demonstration, is a model of practical electron clock.