R4RIN – MCQs, Mock Tests | VHDL VHDL Mcq

What does modeling type refer to?

1. Type of ports in entity block of VHDL code
2. Type of description statements in architecture block of VHDL code
3. Type of data objects
4. Type of Signals

✅ Correct Answer: 2

Which of the following is not a type of VHDL modeling?

1. Behavioral modeling
2. Dataflow modeling
3. Structural modeling
4. Component modeling

✅ Correct Answer: 4

In behavioral modeling, what do descriptive statements describe?

1. How the system performs on given input values
2. How e design is to be implemented
3. Netlist
4. Concurrent execution

✅ Correct Answer: 1

In behavioral modeling, what do descriptive statements describe?

1. How the system performs on given input values
2. How e design is to be implemented
3. Netlist
4. Concurrent execution

✅ Correct Answer: 1

Which of the following statement is used in structural modeling?

1. portmap()
2. process()
3. if-else
4. case

✅ Correct Answer: 1

What is the basic unit of behavioral description?

1. Structure
2. Sequence
3. Process
4. Dataflow

✅ Correct Answer: 3

Which of the following modeling style follows the sequential processing of instructions?

1. Dataflow modeling
2. Behavior modeling
3. Structural modeling
4. Component modeling

✅ Correct Answer: 2

_________ modeling uses logic gates and basic blocks to describe the functionality of system.

1. Behavioral
2. Structural
3. Dataflow
4. Component

✅ Correct Answer: 3

Which of the following architecture defines the data flow modeling of ‘and’ gate?

1. ARCHITECTURE and_1 OF and_gate IS begin y <= a AND b; end and_1;
2. ARCHITECTURE dataflow OF and_gate IS Process(a, b, y); begin y <= a AND b; end dataflow;
3. ARCHITECTURE and_1 OF and_gate IS begin IF(a = ‘1’ and b = ‘1’) THEN c <= 1; ELSE c &lt;= ‘0’; end and_1;
4. ARCHITECTURE dataflow OF and_gate IS begin y <= a AND b; end and_1;

✅ Correct Answer: 1

Refer to the code given below, which type of modeling is used to describe the system? ARCHITECTURE and_1 OF and_gate IS begin process(a, b, y) begin IF(a = ‘1’ and b = ‘1’) THEN y <= ‘1’; ELSE y <=’0’; end IF; END process; END and_1;

1. Structural
2. Component
3. Dataflow
4. Behavioral

✅ Correct Answer: 4

Which logic function is described in the code given below? ARCHITECTURE my_func OF my_logic IS begin process(a, b, y) begin IF(a = ‘0’ and b = ‘0’) THEN y <= ‘0’; ELSIF (a = ‘1’ and b= ‘1’) THEN y<= ‘0’; ELSE y <= ‘1’; END if; END process; END my_func;

1. AND
2. EXOR
3. OR
4. EXNOR

✅ Correct Answer: 2

Which modeling style does the following code represents? Architecture my_logic OF logic_func IS Component gate_1 PORT (b1, b2 : IN BIT; s : OUT BIT); END component; Component gate_2 IS PORT (b1,b2 : IN BIT; C : OUT BIT); END component; SIGNAL a, b, sum, carry : BIT; begin EXOR : gate_1 portmap (a, b, sum); AND : gate_2 portmap (a,b ,carry); END my_logic

1. Structural
2. Component
3. Behavior
4. Dataflow

✅ Correct Answer: 1

Ports are known as _________ to the component.

1. Structure
2. Behavior
3. Function
4. Interface

✅ Correct Answer: 4

What is the use of a function called port map()?

1. Component declaration
2. Defining identifiers
3. Component instantiation
4. Defining inputs and outputs

✅ Correct Answer: 3

The signal assignment is considered as a ________

1. Concurrent statement
2. Sequential statement
3. Subprogram
4. Package declaration statement

✅ Correct Answer: 1

How can we use an assignment statement as a sequential assignment?

1. By using keyword WAIT
2. By using a delay mechanism
3. By using conditional statements
4. By using it in any process

✅ Correct Answer: 4

The sequential assignment statement is activated, whenever ________

1. The waveform associated changes its value
2. The process is terminated
3. The execution is scheduled
4. The value of the target is needed

✅ Correct Answer: 2

The concurrent assignment statement is activated whenever ______

1. The execution is scheduled
2. The value of the target is needed
3. The waveform associated changes its value
4. The process is terminated

✅ Correct Answer: 3

The concurrent assignment statement is activated whenever ______

1. The execution is scheduled
2. The value of the target is needed
3. The waveform associated changes its value
4. The process is terminated

✅ Correct Answer: 3

Which of the following is correct syntax for a signal assignment statement (if {} specifies an optional part)?

1. target <= {delay_mechanism} waveform;
2. target <= delay_mechanism waveform;
3. target <= delay_mechanism {waveform};
4. target <= {delay_mechanism} {waveform} value;

✅ Correct Answer: 1

The conditional assignment statement is a _________ assignment.

1. Sequential
2. Concurrent
3. Selected
4. None of the above

✅ Correct Answer: 2

The conditional assignment statement is a _________ assignment.

1. Sequential
2. Concurrent
3. Selected
4. None of the above

✅ Correct Answer: 2

Delays are generally ignored in ________ assignments statements.

1. Concurrent
2. Conditional
3. Sequential
4. Selected

✅ Correct Answer: 3

Which of the following can’t be a mode for target operand of assignment statement?

1. BUFFER
2. INOUT
3. OUT
4. IN

✅ Correct Answer: 4

Which of the following is a variable assignment statement?

1. <=
2. :=
3. =>
4. ==

✅ Correct Answer: 2

Which of the following is a keyword used for conditional assignment?

1. IF
2. WHEN
3. FOR
4. END

✅ Correct Answer: 2

For a signal used in sequential assignment, it can have _______

1. 1
2. 2
3. 3
4. 4

✅ Correct Answer: 1

The selected concurrent statement is equivalent to ________ sequential statement.

1. If else
2. Loop
3. Wait
4. Case

✅ Correct Answer: 4

Those statement which are placed under ________ are concurrent.

1. Process
2. Function
3. Architecture
4. Procedure

✅ Correct Answer: 3

Process is a _______ statement.

1. Concurrent
2. Sequential
3. Delay
4. Both concurrent and sequential

✅ Correct Answer: 1

If there is more than one process in a VHDL code, How they are executed?

1. One after the other
2. Concurrently
3. According to sensitivity list
4. Sequentially

✅ Correct Answer: 2

Local variables in a process can be declared __________

1. Anywhere within the process
2. After a sequential statement
3. Before the BEGIN keyword
4. After the BEGIN keyword

✅ Correct Answer: 3

Sensitivity list of a process contains __________

1. Constants
2. Signals
3. Variables
4. Literals

✅ Correct Answer: 2

Which of the following statement is used when there are no signals in the sensitive list?

1. WHEN
2. IF ELSE
3. WAIT
4. CASE

✅ Correct Answer: 3

What is the effect of the sensitivity list on the process?

1. Process executes when any of the signal in sensitivity list changes
2. Process executes sequentially when sensitivity list is specified
3. If there is no sensitivity list, then the process will not execute
4. Helps in simulation

✅ Correct Answer: 1

If no signal in the sensitivity list is changed, then how many times the process will be executed?

1. 3
2. 2
3. 1
4. 0

✅ Correct Answer: 3

Which of the following statements can be seen as sequential equivalent to the selected concurrent assignment?

1. IF ELSE
2. WAIT
3. WHEN
4. CASE

✅ Correct Answer: 4

A __________ can’t be declared inside a process.

1. Signal
2. Variable
3. Constants
4. Subprograms

✅ Correct Answer: 1

The process can be __________ by using WAIT statements.

1. Suspended
2. Resumed
3. Suspended as well as resumed
4. Cannot be determined

✅ Correct Answer: 3

A postponed process runs when ___________

1. All the other processes have completed
2. After completion of one particular process
3. Concurrently with all other processes
4. First of all processes

✅ Correct Answer: 1

Which of the following statement can’t be used inside a process?

1. WAIT
2. IF ELSE
3. Variable declaration
4. PORT MAP

✅ Correct Answer: 4

The value of y is initially 1 and it is changed after one delta cycle to 0. How many delta cycles (starting from the beginning) will be taken to change the initial value of z, refer to the process given below? PROCESS (y) BEGIN x &lt;=y; z &lt;= NOT y; END PROCESS

1. 1
2. 2
3. 3
4. 4

✅ Correct Answer: 2

A combinational process must have all the _________ signals in its sensitivity list.

1. Input
2. Output
3. Declared
4. Used

✅ Correct Answer: 1

Which of the following circuit can’t be described without using a process statement?

1. Multiplexer
2. D flip-flop
3. Decoder
4. Comparator

✅ Correct Answer: 2

Which of the following signal uses keyword EVENT?

1. Variables
2. Output
3. Input
4. Clock

✅ Correct Answer: 4

Refer to the code given below, what kind of circuit is designed? SIGNAL x : IN BIT; SIGNAL y : OUT BIT; SIGNAL clk : IN BIT; PROCESS (clk) BEGIN IF (clk’EVENT and clk = ‘1’) y ;&lt= x; END PROCESS

1. Buffer
2. Latch
3. Flip flop
4. Shift Register

✅ Correct Answer: 3

The driver(s) of signal y is _________ PROCESS () BEGIN y &lt;= ‘1’; y &lt;= x; y &lt;= z; END PROCESS;

1. z
2. x
3. x and z
4. 1

✅ Correct Answer: 1

The resolution function is needed to resolve the value of _______ PROCESS () BEGIN y &lt;= x; y &lt;= z; END PROCESS;

1. z
2. y
3. x
4. No x, y and z

✅ Correct Answer: 4

What kind of statement is the IF statement?

1. Concurrent
2. Sequential
3. Assignment
4. Selected assignment

✅ Correct Answer: 2

Which of the following keyword is not associated with IF statement?

1. ELSE
2. THEN
3. ELSIF
4. WHEN

✅ Correct Answer: 4

Which of the following represents the correct order for keywords?

1. IF, THEN, ELSIF, THEN, ELSE
2. IF, ELSE, THEN, ELSIF, THEN
3. IF, ELSIF, THEN, ELSE, THEN
4. IF, THEN, ELSE, THEN, ELSIF

✅ Correct Answer: 1

If the condition of IF statement is an expression, then what should be the type of the result of the expression?

1. Bit
2. Std_logic
3. Boolean
4. Integer

✅ Correct Answer: 3

In the following lines, what should be the value of signal y, if a and b both are at logic high? PROCESS (a, b) BEGIN IF( a XOR b &lt;=’1’) y &lt;= ‘1’; ELSIF (a AND b <= ‘0’) y &lt;= a; ELSE y &lt;= ‘0’; END IF; END PROCESS;

1. a
2. b
3. 0
4. 1

✅ Correct Answer: 3

Which of the following condition has topmost priority?

1. IF
2. ELSIF
3. ELSE
4. THEN

✅ Correct Answer: 1

What logic is described in the following logic? PROCESS (a, b) IF (a = ‘1’ AND b = ‘0’ OR a= ’0’ AND b = ‘1’) THEN y &lt;= ‘1’; ELSIF (a = ‘1’ AND b= ‘1’) THEN y &lt;= ‘0’; ELSE y &lt;= ‘0’; END IF

1. EXOR
2. EXNOR
3. AND
4. NOR

✅ Correct Answer: 1

One IF statement can have multiple ___________

1. IF
2. ELSIF
3. ELSE
4. CASE

✅ Correct Answer: 2

If a user gets an error at the time of simulation which is “ the IF statement is illegal” what could be the reason?

1. Using IF statement in architecture body
2. Using IF statement without ELSE
3. Using multiple ELSE statements
4. Using concurrent assignment in the IF

✅ Correct Answer: 1

In a clocked process, IF statement is used to __________

1. To run statements sequentially
2. To use concurrent assignment within process
3. To detect the clock signal
4. To implement sequential circuit

✅ Correct Answer: 3

What will be the output in the following code? ARCHITECTURE my_logic OF my_design IS BEGIN a &lt;= 1; b &lt;= 1; PROCESS (a, b) BEGIN IF (a AND b = 1) THEN output &lt;= a; ELSIF (a OR b = 1) THEN output &lt;= b; ELSE output &lt;= 0; END IF; END PROCESS; END my_logic;

1. 0
2. 1
3. b
4. a

✅ Correct Answer: 4

What is the problem with IF statement?

1. Overlapping of conditions
2. No default value
3. The condition can be Boolean only
4. Restriction on number of ELSE statement

✅ Correct Answer: 1

In which of the following statements, all the branches are equal in priority?

1. IF
2. CASE
3. WAIT
4. LOOP

✅ Correct Answer: 2

In case any of the conditions is not covered by ‘cases’ in the case statement, which of the following keyword can be used to cover all those conditions?

1. ELSE
2. ELSIF
3. REMAINING
4. OTHERS

✅ Correct Answer: 4

CASE is a sequential statement, which is similar to _________ concurrent statement.

1. Concurrent assignment
2. PORT MAP
3. WHEN
4. THEN

✅ Correct Answer: 3

What will be the value of Z in the following code? ENTITY case_1 IS Port (a, b, c, y : IN INTEGER range 0 TO 31 z : OUT INTEGER range 0 TO 31) ARCHITECTURE example OF case_1 IS BEGIN y &lt;= 2; a &lt;= 4; b &lt;= 5; c &lt;=6; PROCESS(a, b, c, y) BEGIN CASE y+1 IS WHEN 1 =&gt; z &lt;= a; WHEN 2 =&gt; z &lt;= b; WHEN 3 =&gt; z &lt;= c; WHEN OTHERS =&gt; Z &lt;= 0; END CASE; END PROCESS; END example;

1. 2
2. 4
3. 5
4. 6

✅ Correct Answer: 4

What should be the type of choices in the CASE statement?

1. Boolean
2. Integer
3. Same as expression
4. No restriction on the type

✅ Correct Answer: 3

If one wants to perform no action, when any condition is true, then which of the following keyword can be used?

1. NO OPERATION;
2. NOP;
3. NULL;
4. NEXT

✅ Correct Answer: 3

It is not possible to use range with _________ types.

1. Integer
2. BIT_VECTOR
3. STD_LOGIC
4. Natural

✅ Correct Answer: 2

The CASE statement in VHDL is similar to _________ in C.

1. Switch
2. If else
3. Pointers
4. Arrays

✅ Correct Answer: 1

Which of the following operators can’t be used in the choices of a CASE?

1. Arithmetic
2. Logical
3. Relational
4. Every type of operators can be used

✅ Correct Answer: 3

What is the main use of a CASE statement?

1. To design multiplexers
2. To design Comparators
3. To design Flip flop
4. To design state machines

✅ Correct Answer: 4

Which of the following is most complex?

1. IF THEN ELSE
2. Nested IF THEN ELSE
3. ELSIF
4. CASE

✅ Correct Answer: 2

Which of the following is not a legal statement used Ii CASE?

1. WHEN 1 =>
2. WHEN 1 TO 3 =>
3. WHEN 1|3 =>
4. WHEN 1 THEN

✅ Correct Answer: 4

A loop statement is used where we needs to ________

1. Select one from many choices
2. Check a condition
3. Repeat the statements
4. Choose one from two cases

✅ Correct Answer: 3

Loop is a ________ statement.

1. Concurrent
2. Sequential
3. Assignment
4. Functional

✅ Correct Answer: 2

What is the use of FOR loop?

1. To repeat the statement finite number of times
2. To repeat the statement until any condition holds true
3. To repeat the statements for infinite time
4. To repeat statements inside until any condition is false

✅ Correct Answer: 1

What is the use of WHILE loop?

1. To repeat the statement finite number of times
2. To repeat the statement until any condition holds true
3. To repeat the statements for infinite time
4. To repeat statements inside until any condition is false

✅ Correct Answer: 2

What does the next statement in loops do?

1. Skips the current iteration
2. Starts the next loop by ending the current
3. Exits the loop
4. Skips the next line of the loop

✅ Correct Answer: 1

What is the syntax to use the NEXT statement?

1. NEXT condition loop_label
2. NEXT loop_label WHEN condition
3. loop_label NEXT WHEN condition
4. loop_label NEXT condition

✅ Correct Answer: 2

The correct syntax for using EXIT in a loop is ___________

1. EXIT loop_label WHEN condition;
2. EXIT WHEN condition loop_label;
3. loop_label WHEN condition EXIT
4. EXIT WHEN loop_label condition

✅ Correct Answer: 1

FOR loop uses a loop index, the type of loop index is _________

1. STD_LOGIC_VECTOR
2. BIT_VECTOR
3. INTEGER
4. REAL

✅ Correct Answer: 3

Where do we declare the loop index of a FOR LOOP?

1. Entity
2. Architecture
3. Library
4. It doesn’t have to be declared

✅ Correct Answer: 4

A FOR loop is inside a WHILE loop. Inside the FOR loop, the EXIT statement is used in such a way that after 4 iterations, it will execute. After the execution of EXIT statement, the control will be passed ________

1. Outside the FOR loop
2. Outside the WHILE loop
3. At the next iteration of WHILE loop
4. At the next iteration of FOR loop

✅ Correct Answer: 1

On what side of the assignment statement, one can use a loop index?

1. Left
2. Right
3. Left or Right
4. Loop index can’t be used in an assignment

✅ Correct Answer: 2

The FOR loop is not synthesizable if it contains ______ statement. a) d)

1. WHEN
2. THEN
3. WAIT
4. IF

✅ Correct Answer: 3

The FOR loop is not synthesizable if it contains ______ statement.

1. WHEN
2. THEN
3. WAIT
4. IF

✅ Correct Answer: 3

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VHDL Mcq – Types of VHDL Modelling