Demonstrations for tim8 as pwm output operation.

example function:
	PA6 as brake signal putin  PA12(IOPORT_CH3) and EBUS IO brake
	Event0/Event1
	PA10 toggle in update interrupt 
	PA8 toggle in brake interrupt 
	
	
1. PWM output example ：
	FCLK：96M。
	PWM freq：16K
	
	timer cycle calculate formula：(period+1)/Freq *(Prescaler+1)
								= (2999+1)/96000000 * (0+1)
								=  0.00003125s
	centermpde ，cycle*2  = 0.00003125s * 2  = 0.0000625s
				 freq     = 1/0.0000625 = 16000HZ

2、pwm wave config：
	brake idle state：all high level
	duty cycle： 50%
	PWM mode：PWM0
	polar：   low level
	deadtime：   2us
	deadtime parameter ：0xA0
	use deadtime formula：：DTG[7:5]=10X：DT=(64+DTG[5:0])*tdtg，tdtg=2*tDTS。
							DT = (64+0x20)*2/96000000
							   = 0x000002s
