学习《单键触发8位二进制累加计数器》该程序的目的是让大家熟悉输入、输出端口的使用，该程序的功能是把演示板当做一个按键计数器。刚刚接通电源时，8只发光二极管都不亮。表示计数器初值为0，当按下开关S3（RB0）时，计数器的值加1，发光二极管D3点亮，表示值1，然后松开按钮；再次按下开关S3（RB0）时，计数器的值又加1，发光二极管D4点亮，表示值2，依次类推，反复循环。-Learn " Speed ​ ​ trigger 8-bit binary up-counter"　The purpose of the program is to make people familiar with the use of input and output ports, the functionality of the program as a key counter demo board. Just power, eight light-emitting diodes are lit. Said counter initial value of 0, when the switch is pressed S3 (RB0), the value of the counter and a light-emitting diode D3 lit, indicates a value of 1, and then release the button　once again press the switch S3 (RB0) counter value and plus 1, the light emitting diode D4 lights up, indicating that the value 2, etc., repeated cycle.