Week 8

Question 1

max gate delay

Answer 1

add max number of gates needed to reach output

Question 2

replicate the adder multiple times

Answer 2

ripple carry adder

Question 3

_____ circuits maintain the current state they are in

Answer 3

sequential

Question 4

_____ is one of the most basic sequential circuits

Answer 4

latch

Question 5

latch has an extra input called a _____

Answer 5

enable line

Question 6

input is frozen when…

Answer 6

enable line is 0

Question 7

propogation delay:

Answer 7

delay occurs between time input changes & output changes

Question 8

flip flops:

Answer 8

depend on previous input
depend on current input
cannot be constructed from single gate, but rather pair of latches
changes output every “1” bit // only switches when input “rises”

Question 9

identity circuit

Answer 9

2 NOT gates, output = 2 T input, where T = 1 gate delay

Question 10

feedback

Answer 10

joining a circuit back to itself, output is connected to input

Question 11

S’R’ latch

Answer 11

set or reset logic value of output

Question 12

Remember (S’R’ table)

Answer 12

S’ = 1, R’ = 1, Q(t) = X, Q(t+1) = Q(t) (No change, quite literally remember the state Q(t) is in)

Question 13

Set (S’R’ table)

Answer 13

S’ = 0, R’ = 1, Q(t) = X, Q(t+1) = 1 (Start remembering 1)

Question 14

Reset (S’R’ table)

Answer 14

S’ = 1, R’ = 0, Q(t) = X, Q(t+1) = 0 (Start remembering 0)

Question 15

(avoid) (S’R’ table)

Answer 15

S’ = 0, R’ = 0, Q(t) = X, Q(t+1) = Q’(t+1) = 1 (bad behavior)

Question 16

combinatorial

Answer 16

function of logic outputs

Question 17

sequential:

Answer 17

function of current and historic logic outputs (time)

Question 18

What values of S’R’ do you need for…

Have: Q(t) = 1
Want: Q(t+1) = 1

Answer 18

S’ = X R’ = 1

Can be either Remember or Set, so S’ doesn’t matter as long as R’ is 1

Question 19

What values of S’R’ do you need for…

Have: Q(t) = 0
Want: Q(t+1) = 1

Answer 19

S’ = 0 R’ = 1

Set to 1

Question 20

What values of S’R’ do you need for…

Have: Q(t) = 1
Want: Q(t+1) = 0

Answer 20

S’ = 1 R’ = 0

Reset to 0

Question 21

What values of S’R’ do you need for…

Have: Q(t) = 0
Want: Q(t+1) = 0

Answer 21

S’ = 1, R’ = X

Can be either Remember or Reset, so R’ doesn’t matter as long as S’ is 1