While the master–slave flip-flop is also triggered on the edge of a clock, its components are each triggered by clock levels. so the last variation of input can effect output signals and the first mentioned problem would be resolved. What happens during the entire HIGH part of clock can affect eventual output. It means that data is entered on the rising edge of the clock pulse, but the output does not reflect the change until the falling edge of the clock pulse. Edge-triggered Flip-Flop Contrast to Pulse-triggered SR Flip-Flop Pulse-triggered: Read input while clock is 1, change output when the clock goes to 0. When the clock signal returns to low (1 to 0), the output of the "slave" latch is "locked", and the value seen at the last rising edge of the clock is held while the "master" latch begins to accept new values in preparation for the next rising clock edge. This allows the signal captured at the rising edge of the clock by the now "locked" master latch to pass through the "slave" latch. Nearly simultaneously, the twice inverted "enable" of the second or "slave" D latch transitions from low to high (0 to 1) with the clock signal. As the clock signal goes high (0 to 1) the inverted "enable" of the first latch goes low (1 to 0) and the value seen at the input to the master latch is "locked". This allows the "master" latch to store the input value when the clock signal transitions from low to high. Level sensitive FFs have 2 timing problems:ġ) possibility of accruing multile variation in the output signal at one clock stage.Ģ) problems due to short or long clock cycles.įor a positive-edge triggered master–slave D flip-flop, when the clock signal is low (logical 0) the "enable" seen by the first or "master" D latch (the inverted clock signal) is high (logical 1). Master Slave FF (Flip Flop) is used to solve one of the problems in level sensitive FFs.