适用于S3C2410，ADS1.2编译通过。用按键S4控制LED3和LED4的亮灭：按下S4不动时，LED3和LED4同时闪烁点亮，放开S4后，LED3和LED4同时熄灭。-applicable to the S3C2410, ADS1.2 compile. S4 control with illuminated keypad and bright eliminate LED4 : press S4 fixed, LED4 illuminated and flashing lights while 300 S4, and indicates the same time LED4 extinguished.