八、单脉冲的形成在数字设备中,有时候需要用到单脉冲。例如让机器开始工作,就得发一个“起动”信号;要把数据手动打入到寄存器中去,就得有一个打入脉冲,等等。产生单脉冲最简单的方法是用一个扳键,如图100所示。平时 A 点为高电位,当扳键按下时,A 点由高电位变为低电位;一松手时,扳键自动返回,A点又由低电位变成高电位。这样在你按下扳键和松手的过程中,A 点便输入了一个负方波。但是,由于扳键的触点在通断的过程中往往会发生抖动,这样在 A 点得到的电压波形实际上如图101所示。方波的前沿部份会出现许多“毛刺”,相当于连续输入 Eight, the formation of a single pulse In digital devices, sometimes need to use a single pulse. For example, let the machine start working, you have to send a “start” signal; to manually enter the data into the register, you have to have a pulse, and so on. The simplest way to generate a single pulse is to use a pull button, as shown in Figure 100. Usually point A is high potential, when the pull button is pressed, A point from high potential to low potential; a let go, the pull button automatically returns, A point from low potential to high potential. So when you press the pull button and let go of the process, A point will enter a negative square wave. However, since the contacts of the wrench are often jittered during turn-on and turn-off, the resulting voltage waveform at point A is actually as shown in Figure 101. There are many “glitches” in the front part of the square wave, which are equivalent to continuous input