说明：  本文在两片采用不同主频的ＰＩＣ单片机（Ａ机时钟频率为６ＭＨｚ，使用口线ＲＢ６；Ｂ机时钟频率为４ＭＨｚ，使用口线ＲＢ４）之间实现异步通讯
(In this paper, two different frequency of the PIC Singlechip (A machine clock frequency of 6MHz, the use of the mouth line RB6 B machine clock frequency of 4MHz, the use of the mouth line RB4) asynchronous communication between)