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CS151: Digital Design

Chapters 4, 5

Review

CS 151 2

Question 1

Design a combinational circuit for a Roller-Coaster ride in an amusement park. The design should include a truth table, simplified Boolean function(s), and logic diagram.The Roller-Coaster Safety System has three sensors:

Speed: this sensor will generate a signal if the roller-coaster vehicle exceeds the speed limit

Safety: this sensor will generate a signal if one of the seatbelts is unbuckled

Stability: this sensor will generate a signal if the roller-coaster moves off the tracks

The Roller-Coaster Safety System has two output features: Slow: this will be activated to slow down the vehicle if the Speed

sensor was on. Shut-down: this will be activated to stop the roller-coaster if at least

two sensors were on.

CS 151 3

4 X 1 Line MUX Transmission Gate Multiplexer

S0

S1

I0

I1

I2

I3

Y

TG(S0 5 0)

TG(S1 5 0)

TG(S1 5 1)

TG(S0 5 1)

TG(S0 5 0)

TG(S0 5 1)

S1S0Y

00I0

01I1

10I2

11I3

CS 151 4

Question 2

Construct an 8-to-1-line multiplexer with enable input using transmission gates.

S2S1S0Y

000I0

001I1

010I2

011I3

100I4

101I5

110I6

111I37

CS 151 5

8 x 1 MUX

Y

CS 151 6

Question 3

Show that a positive logic NAND gate is a negative logic NOR gate.

CS 151 7

Question 4

Design an Excess-3-to-BCD code converter, that gives output code 0000 for all invalid input combinations. Your design should include the truth table and simplified equations for each possible output. Note that possible inputs range from the exess-3 codes 0011 (0 decimal) to 1100 (9 decimal).