Chapter 5 Sequential Circuits Sequential Circuits Combinational Circuits

Chapter 5 Sequential Circuits

Sequential Circuits • Combinational Circuits + Storage element • output depends both on previous state and input Fig. 5 -1

Storage element • t. G the delay • the stored information can’t be changed Fig. 5 -2

Synchronous clocked sequential circuit Use flip-flop Fig. 5 -3

SR latch • A storage element can maintain a binary state indefinitely, until directed by an input signal to switch states. • The most basic storage elements are latches. Fig. 5 -4

Simulation for SR latch Fig. 5 -5

- latch Fig. 5 -6

- latch with control Fig. 5 -7

D (Data) latch Fig. 5 -8

Flip-Flops �A change in value on the control input allows the state of a latch in a flip-flop to switch. �This change is called a trigger �The trigger enable (trigger) the flip-flops �See Fig. 5 -3 for sequential circuits �A present (original) and next (new) state occur in flipflop before and after the trigger, respectively �The most important element in sequential circuits �Can be derived from latch

SR Master-Slave flip-flop Fig. 5 -9

Simulation for SR Master-Slave flip-flop • Pulse trigger • Pulse in the inputs SR will results wrong output Fig. 5 -10

Negative -edge-trigger Flip-Flop Fig. 5 -11

Positive -edge-trigger Flip-Flop

Symbols Fig. 5 -13

Symbols Fig. 5 -14