D Flip Flop can be built from 2 back-to-back D latch controlled by complementary clocks. The first latch L1 which is called Master and the second latch L2 is called Slave.
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D Flip Flop |
When CLK = 0, the master latch is transparent, and slave is opaque. When CLK = 1, the master is opaque, and slave is transparent. Hence whatever value was at D immediately before the clock rises from 0 to 1 gets copied to Q immediately after the clock rises. At all other times, Q holds its previous value as there is always an opaque latch that blocks the path between D and Q. So, it can be concluded that D Flip Flop Copies D to Q on the rising edge of the clock and remembers its state at all other times. This D FF can also be called as a master slave FF, an edge triggered FF, or a positive edge triggered FF.
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| D Flip Flop Symbol |