Digital logic gets really interesting when we connect the output of gates back to an input. The SR latch is one of the most basic memory circuits that we can build on to make counters, registers, and all sorts of other interesting things.
SR 对应 set reset
或门:
先观察右边的或门，查看真值表
按下a亮灯 松开a 灯亮的状态仍然保持
通过74LS32实现
锁存器
SR 锁存器
