Chapter 5

Question 1

sequential circuit

Answer 1

outputs are a function of the inputs and the state of the storage elements (aka past inputs)

Question 2

synchronous sequential circuits

Answer 2

behavior can be defined from the signals at discrete instants of time, uses a clock signal

Question 3

asynchronous sequential circuit

Answer 3

behavior depends on input signals at any instant of time and the order in which the inputs change
- use time delay storage elements

Question 4

latches

Answer 4

• storage elements that work with signal levels

Question 5

level sensitive devices

Answer 5

operate with signal levels (0 or 1)

Question 6

edge sensitive devices

Answer 6

operate with signal transitions (high to low or low to high)

Question 7

flip flops are ______ sensitive devices

Answer 7

edge

Question 8

S-R Latch

Answer 8

-2 cross coupled NOR or AND gates
- has 2 inputs: S and R

Question 9

S-R latch truth table

Answer 9

S R Q Q’
1 0 1 0 (set)
0 1 0 1 (reset)
0 0 x x (Q doesnt change)
1 1 0 0 (forbidden)

Question 10

S-R latch with control input

Answer 10

third input, En, is NANDed with both inputs before going into S-R latch
if En is 0, there is no change

Question 11

D-Latch

Answer 11

gets rid of forbidden state of S-R latch, has only 2 inputs (D and En), D fulfills role of S and R by going through a not gate to become R

Question 12

D-Latch truth table

Answer 12

D Next
0 Reset
1 Setq

Question 13

flip flop

Answer 13

• 1 bit memory element

Question 14

the output-input relationship of a FF is defined by a _______ or _______

Answer 14

characteristic table or characteristic equation

Question 15

direct inputs

Answer 15

• inputs that set or reset their states independent of the clock, so come in through bottom of diagram

Question 16

D flip flop construction

Answer 16

• master-slave flip flop
• uses two D latches and an inverter
• Output of flip flop 1 fed to FF2
• regular clock enters FF1(master) and then is inverted before entering FF2 (slave)

Question 17

D FF

Answer 17

• input enters master latch when clock goes up, then when clock goes down that information transfers to the slave latch/final output

Question 18

draw a JK flipflop

Answer 18

• J, Q’ and Clk enter a NAND gate (output w1)
• K, Q, and clk enter a NAND gate (output w2)
• w1 and Q’ enter a NAND gate (output Q)
• w2 and Q enter a NAND gate (output Q’)

Question 19

T Flip Flop from JK

Answer 19

a j-k flip flop when J and K are tied together

Question 20

basic principle of T FF

Answer 20

complementing or not complementing last state

Question 21

Latches are faster or slower than FF

Answer 21

faster

Question 22

form of state equations

Answer 22

A(t+1) = Ax+B’x

Question 23

is the output of a sequential circuit in the form y(t+1) or y(t)

Answer 23

y(t)

Question 24

parts of a state table

Answer 24

present state, input, next state, output

Question 25

state diagrams have a form x/x on the arrow, which is each?

Answer 25

input/output

Question 26

what is in the circles on state diagrams

Answer 26

state of flip flops

Question 27

steps of analysis of clocked sequential circuit

Answer 27

circuit diagram
state equations
state table
state diagram

Question 28

Moore machine

Answer 28

output only depends on current states

Question 29

Mealy machine

Answer 29

output depends on current states and inputs

Question 30

what does a characteristic table describe

Answer 30

flip flop operations

Question 31

excitation table def

Answer 31

values of FF inputs for a given state transition

Question 32

sequential circuit design procedure

Answer 32

1. derive state diagram
2. assign binary values to the states
3. obtain binary coded state table
4. choose the type of FF
5. derive input equations using next state values and excitation tables
6. simplify using Kmap
7. draw logic diagram