VIDEO TUTORIALS: The Master Slave D Flipflop
The master-slave D flipflop is actually two D Latches arranged such that the output of one latch (which we call the master latch) drives the second latch (which we call the slave latch). The clock input controls access both to the master D latch and to the slave D latch. When the clock switch is OFF, the door to the master is opened, while at the same time the door to the slave is closed. Since the door to the master D latch is open, the input switch D now controls the master D latch. But at the same time, the slave D latch is not affected.