Flip-Flops

Flip-flops are synchronous, edge-triggered storage elements. They have two stable states and store one state indefinitely until triggered by a clock signal to change.

They are the fundamental building blocks of sequential circuits due to their ability to store information. One flip-flop can store one binary bit of data.

Most flip-flops have asynchronous input lines to set their initial state.

Types of Flip-Flops

D Flip-Flop

A data or delay flip-flop is the most basic form of a flip-flop. It can be used to help construct other, more complex flip-flops.

D Flip-Flop Implementation

This implementation is known as a Master-Slave D Flip-Flop.
It is constructed from two D-latches connected in series with one latch receiving an inverted clock signal compared to the other.

• The master latch is connected to the input D
• The slave latch is connected to output Q
  • Controlled by inverted signal controlling master latch

Only one latch is enabled at any given time. The final output changes during one transition of clock.

A positive-edge triggered D flip-flop uses two inverters, whereas a negative-edge triggered D flip-flop uses only one, as seen above.

The characteristic equation of a D flip-flop is $Q_{next}=D$.

The excitation table of a D flip-flop is:

$Q$	$Q_{next}$	$D$
$0$	$0$	$0$
$0$	$1$	$1$
$1$	$0$	$0$
$1$	$1$	$1$

JK Flip-Flop

T Flip-Flop

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