usb1.1标准协议,包括:ACK:确认信号 ctive Device:正在使用的设备 synchronous Data:异步数据 synchronous RA:异步自适应速率 -usb1.1 standard protocols, including : ACK : confirmation signal Merit Device : The equipment used is synchronous Data : Asynchronous data synchronous RA : as

数字式计时器一般都由震荡器，分频器，译码器及显示几部分组成。其中震荡器和分频器组成标准秒信号发生器，接成各种不同进制的计数器组成计时系统，译码器，显示器组成显示系统，另外一些组合电路组成校时调节系统。-digital timer usually are oscillator, dividers, decoder and display several parts. Which oscillator and divider standard component signal generator s