Demonstrations for tim0 as basetimer operation.

example function：
	PA10 toggle in timer interrupt
	
1. timer interrupt example：
	freq：96M。
	cycle：1MS
	
	timer interrupt calculate formula：(period+1)/Freq *(Prescaler+1)
								   = (47999+1)/96000000 * (1+1)
								   =  0.001s
	
