R-S触发器（锁存） 的应用 +Vcc +Vcc R Erratic transition voltage due to contact bounce Position Position 102 2101 (a)Switch contact bounce (b)Contact-bounce eliminator circuit The Latch as a Contact-Bounce Eliminator A good example of an application of an S-R latch is in the elimination of mechanical switch contact"bounce."When the pole of a switch strikes the contact upon switch closure,it physically vibrates or bounces several times be- fore finally making a solid contact.Although these bounces are very short in duration,they produce voltage spikes that are often not acceptable in a digital system.This situation is il- lustrated in Figure 7-6(a). An S-R latch can be used to eliminate the effects of switch bounce as shown in Figure 7-6(b).The switch is normally in position 1,keeping the R input LOW and the latch RESET. When the switch is thrown to position 2,R goes HIGH because of the pull-up resistor to Vec. and S goes LOW on the first contact.Although S remains LOW for only a very short time before the switch bounces,this is sufficient to set the latch.Any further voltage spikes on the S input due to switch bounce do not affect the latch,and it remains SET.Notice that the output of the latch provides a clean transition from LOW to HIGH,thus eliminating the volt- age spikes caused by contact bounce.Similarly,a clean transition from HIGH to LOW is made when the switch is thrown back to position 1.R-S触发器（锁存）的应用