VHDL Practice Test 9

1. What is the state of PRESET input?

Invalid

Set

Reset

Don’t care

2. The output of the flip-flop _______ when both the input, preset and clear are active low at the same time.

Is set to 1

Becomes X (Don’t care)

Is set to 0

Is controlled by clock

3. Which of the following gate is a universal gate?

EXOR

NAND

AND

EXNOR

4. Which of the following assignment statement is not generally used in the implementation of Boolean functions?

Sequential assignment

Selected assignment

Concurrent assignment

Conditional assignment

5. Which of the following are prime implicants of the following Boolean function?

Y= AB + BC'D’ + BCD'

AB, BC'D', BCD'

A, B, C, D

AB, CD

AB, BD'

6. Which of the following k-map represents the following given function?

y = AB + AB’C + A’BC

vhdl-questions-answers-implementing-logic-functions-vhdl-1-q4a

vhdl-questions-answers-implementing-logic-functions-vhdl-1-q4d

vhdl-questions-answers-implementing-logic-functions-vhdl-1-q4c

vhdl-questions-answers-implementing-logic-functions-vhdl-1-q4b

7. A sequential logic can’t be executed by concurrent statements only.

False

True

8. A user wants to implement a logic by using VHDL. In which he has inputs from two sensors which are smoke sensor and water level detector. If any input is high, he has to turn on the respective alarm. Which of the following is representing the correct code for the given logic?

 ARCHITECTURE alarm_control OF my_home IS
BEGIN
PROCESS(smoke_sensor, water_sensor)
BEGIN
IF(smoke_sensor = ‘1’) THEN fire_alarm = ‘1’;
ELSE fire_alarm = ‘0’;
END IF;
IF(water_sensor = ‘1’) THEN water_alarm = ‘0’;
ELSE water_alarm = ‘1’;
END IF;
END PROCESS;
END alarm_control;

ARCHITECTURE alarm_control OF my_home IS
BEGIN
PROCESS(smoke_sensor, water_sensor)
BEGIN
IF(smoke_sensor = ‘1’) THEN fire_alarm = ‘1’;
ELSE fire_alarm = ‘0’;
END IF;
IF(water_sensor = ‘1’) THEN water_alarm = ‘1’;
ELSE water_alarm = ‘0’;
END IF;
END PROCESS;
END alarm_control;

ARCHITECTURE alarm_control OF my_home IS
BEGIN
PROCESS(smoke_sensor, water_sensor)
BEGIN
IF(smoke_sensor = ‘1’) THEN fire_alarm = ‘0’;
ELSE fire_alarm = ‘1’;
END IF;
IF(water_sensor = ‘1’) THEN water_alarm = ‘1’;
ELSE water_alarm = ‘0’;
END IF;
END PROCESS;
END alarm_control;

ARCHITECTURE alarm_control OF my_home IS
BEGIN
PROCESS(smoke_sensor, water_sensor)
BEGIN
IF(smoke_sensor = ‘0’) THEN fire_alarm = ‘1’;
ELSE fire_alarm = ‘0’;
END IF;
IF(water_sensor = ‘0’) THEN water_alarm = ‘1’;
ELSE water_alarm = ‘0’;
END IF;
END PROCESS;
END alarm_control;

9. What type of inputs is preset and clear?

Output

Data input

Clock input

Control input

10. How many types of resets are there in hardware design?

Three

One

Four

Two