说明：  在JX44B0实验箱上实现功能： 按外部中断按扭，LED数码管依次在不同的段数码管上显示0～9及两个英文单词“HELLO”，“BaLL”。再按一次外部中断按扭,LED数码管灭，如此循环反复。
(In JX44B0 achieve functional test case: according to the external interrupt button, LED digital tube turn in a different segment LED display 0 to 9 and the two English words " HELLO" , " BaLL" . Then an external interrupt button, LED digital tube off, so the cycle repeated.)