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VHDL Multiple-Choice Questions (MCQs)

VHDL stands for VHSIC Hardware Description Language, it is one of the commonly used Hardware Description Languages (HDL) in digital circuit design and is used for system design, modeling, and verification before synthesis into hardware.

VHDL MCQs: This section contains VHDL Multiple-Choice Questions with Answers. These MCQs are written for beginners as well as advanced, practice these MCQs to enhance and test the knowledge of VHDL.

List of VHDL MCQs

1. What is the full form of EDA in terms of VHDL?

  1. Electronic Design Automation
  2. Electrical Data Automation
  3. Electronic Data Auto-collection
  4. Electrical Design Adapter

Answer: A) Electronic Design Automation.

Explanation:

EDA stands for Electronic Design Automation.

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2. The act of building a model or representation of a digital circuit or system in order to forecast its behaviour and evaluate its usefulness is known as ____.

  1. Implementation
  2. Simulation
  3. Verification
  4. Synthesis

Answer: B) Simulation

Explanation:

The act of building a model or representation of a digital circuit or system in order to forecast its behaviour and evaluate its usefulness is known as simulation.

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3. The process of validating that a digital design satisfies its functional and performance criteria is referred to as ____.

  1. Implementation
  2. Simulation
  3. Verification
  4. Synthesis

Answer: C) Verification

Explanation:

The process of validating that a digital design satisfies its functional and performance criteria is referred to as verification.

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4. The process of converting a high-level hardware description language (HDL) design, such as VHDL, into a lower-level representation, often a gate-level netlist, is known as ____.

  1. Implementation
  2. Simulation
  3. Verification
  4. Synthesis

Answer: D) Synthesis

Explanation:

The process of converting a high-level hardware description language (HDL) design, such as VHDL, into a lower-level representation, often a gate-level netlist, is known as synthesis.

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5. Which of the following tools are used to create physical designs and deploy digital systems?

  1. Verification tools
  2. Place and route tools
  3. Time analysis tools
  4. Synthesis tools

Answer: B) Place and route tools

Explanation:

Place and route tools are used to create physical designs and deploy digital systems.

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6. VHDL code is converted into a gate-level representation or netlist by which of the following tools?

  1. Verification tools
  2. Place and route tools
  3. Time analysis tools
  4. Synthesis tools

Answer: D) Synthesis tools

Explanation:

VHDL code is converted into a gate-level representation or netlist by synthesis tools.

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7. Which of the following is not an example of a synthesis tool?

  1. Yosys
  2. Cadence Genus
  3. Prime time
  4. Xilinx Vivado HLS

Answer: C) Prime time

Explanation:

Prime Time is a popular static timing analysis tool.

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8. Which of the following statement is True?

  1. A netlist file is a pictorial representation of the connectivity and logic of a digital circuit
  2. A netlist file is a written representation of the connectivity and logic of a digital circuit

Answer: B) A netlist file is a written representation of the connectivity and logic of a digital circuit.

Explanation:

A netlist file is a written representation of the connectivity and logic of a digital circuit.

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9. Is there any visual or graphical information in a netlist file?

  1. Yes
  2. No

Answer: B) No

Explanation:

There is no visual or graphic information in a netlist file.

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10. Does HDLs emphasize the concept of abstraction?

  1. Yes
  2. No

Answer: A) Yes

Explanation:

Both HDLs and OOP emphasize the idea of abstraction.

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11. Does HDLs encourage modularity and reusability in design and development?

  1. Yes
  2. No

Answer: A) Yes

Explanation:

An HDL promotes modularity and reusability just as OOP does.

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12. An HDL takes which of the following approaches?

  1. Structure and behavioral approach
  2. Object-oriented approach
  3. Master-servant approach

Answer: A) Structure and behavioral approach

Explanation:

HDL takes the structure and behavioral approach.

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13. Verilog enables which modeling techniques?

  1. Structural modeling techniques
  2. Behavioural modeling techniques
  3. Both

Answer: C) Both

Explanation:

Verilog enables structural as well as behavioral modeling techniques.

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14. Can the user specify data types in Verilog?

  1. Yes
  2. No

Answer: B) No

Explanation:

No, the user cannot specify data types in Verilog.

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15. VHDL ____ represent a component's external behavior and interface.

  1. Port
  2. Architecture
  3. Signal
  4. Entity

Answer: D) Entity

Explanation:

VHDL entities represent a component's external behavior and interface.

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16. Using VHDL ____, one can transfer data between components or inside them.

  1. Package
  2. Signal
  3. Port
  4. Component

Answer: B) Signal

Explanation:

Using VHDL signals, one can transfer data between components or inside them.

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17. Port name in VHDL is ____.

  1. Case sensitive
  2. Case insensitive

Answer: B) Case insensitive

Explanation:

The port name is case insensitive.

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18. Which of the following things is True, when it comes to writing up a port name?

  1. It always begins with a number
  2. It always begins with a symbol
  3. It always begins with a letter
  4. It always begins with a letter and symbol

Answer: C) It always begins with a letter.

Explanation:

The port number always begins with a letter.

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19. In VHDL, a ____ is a grouping of related declarations such as data types, constants, and functions that may be shared and utilized across different design units.

  1. Components
  2. Testbench
  3. Concurrent statements
  4. Package

Answer: D) Package

Explanation:

In VHDL, a package is a grouping of related declarations such as data types, constants, and functions that may be shared and utilized across different design units.

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20. Which of the following in VHDL specifies the internal implementation and behavior of a design component?

  1. Port
  2. Architecture
  3. Signal

Answer: B) Architecture

Explanation:

An architecture in VHDL specifies the internal implementation and behavior of a design component.

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21. To specify parameters that can be supplied to VHDL entities, ____ are employed.

  1. Declarations
  2. Port numbers
  3. Packages
  4. Generics

Answer: D) Generics

Explanation:

To specify parameters that can be supplied to VHDL entities, generics are employed.

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22. Which keyword is used to specify ports?

  1. Port_name
  2. Value_port
  3. Port
  4. Pt

Answer: C) Port

Explanation:

The port keyword is used to specify ports.

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23. How many types of ports are there in VHDL?

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

Answer: B) 4

Explanation:

There are four types of ports in VHDL:

  • in
  • out
  • inout
  • buffer

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24. An entity declaration begins with which of the following keyword?

  1. Start Entity
  2. Begin Entity
  3. Ent
  4. Entity

Answer: D) Entity

Explanation:

An entity declaration begins with the keyword entity.

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25. The entity declaration is ended with which of the following keyword?

  1. Finish Entity
  2. Over
  3. End entity
  4. Close entity

Answer: C) End entity

Explanation:

The entity declaration is ended with the keyword 'end entity'.

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26. Multi-bit digital values are represented using ____.

  1. Standard Logic Signals (std_logic)
  2. Standard Logic Vectors (std_logic_vector)
  3. Integer Signals
  4. Boolean Signals

Answer: B) Standard Logic Vectors (std_logic_vector)

Explanation:

Multi-bit digital values are represented using standard logic vectors.

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27. Generics are declared in the ____ declaration part of a VHDL design.

  1. Port declaration
  2. Configuration
  3. Component
  4. Entity

Answer: D) Entity

Explanation:

Generics are declared in the entity declaration part of a VHDL design.

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28. The ____ keyword in VHDL enables the creation of custom user-defined types.

  1. Custom
  2. Type
  3. Use
  4. User

Answer: B) Type

Explanation:

The type keyword in VHDL enables the creation of custom user-defined types.

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29. An architecture declaration begins with the keyword ____.

  1. Archi
  2. Body
  3. Implementation
  4. Architecture

Answer: D) Architecture

Explanation:

An architecture declaration begins with the keyword architecture.

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30. Which of the following statements defines the sequential behavior of an architecture?

  1. Concurrent signal assignment
  2. Case statement
  3. Process statements

Answer: C) Process statements

Explanation:

Process statements define the sequential behavior of an architecture.

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31. Which of the following cannot be used as the name of the architecture in VHDL?

  1. Architecture
  2. Architecturee1
  3. Archii1
  4. Arch00

Answer: A) Architecture

Explanation:

We cannot use keywords as the name; therefore, we cannot use architecture as the name.

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32. Which of the following VHDL object are utilized throughout processes to store temporary values?

  1. Constant
  2. Parameters
  3. Files
  4. Variables

Answer: D) Variables

Explanation:

Variables are utilized throughout processes to store temporary values.

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33. What is the difference between parameters and constants?

  1. Parameters are similar to constants except that their values can be altered at instantiation
  2. Parameters are similar to constants except that their values cannot be altered at instantiation

Answer: A) Parameters are similar to constants except that their values can be altered at instantiation.

Explanation:

Parameters are similar to constants except that their values can be altered at instantiation or through generics.

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34. Signals are assigned by using which of the following assignment operator?

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

Answer: D) <=

Explanation:

Signals are assigned by the assignment operator "<=".

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35. How many types of Modelling styles are there in VHDL?

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

Answer: C) 4

Explanation:

Mainly there are four types of modeling styles on VHDL:

  • Structural Modelling
  • Behavioural Modelling
  • Dataflow Modelling
  • Mixed-Level Modelling

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36. Which of the following modeling is concerned with expressing a design's functioning and behavior without explicitly stating its structure?

  1. Structural Modelling
  2. Behavioural Modelling
  3. Dataflow Modelling
  4. Mixed-Level Modelling

Answer: B) Behavioural Modelling

Explanation:

Behavioural modeling is concerned with expressing a design's functioning and behavior without explicitly stating its structure.

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37. Which of the following operator(s) tests if operands are not equal?

  1. Not Equal
  2. !=
  3. /=
  4. ~=

Answer: C) /=

Explanation:

/= operator is used to test if operands are not equal.

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38. A ____ type can combine elements of different data types to create a composite type.

  1. Array
  2. Record
  3. Files
  4. Variables

Answer: B) Record

Explanation:

A record type can combine elements of different data types to create a composite type.

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39. Which of the following operator is used as a concatenation operator?

  1. ++
  2. $
  3. *
  4. &

Answer: D) &

Explanation:

& is known as a concatenation operator in VHDL.

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40. Which of the following keyword is used to explicitly transform data from one type to another?

  1. Transform
  2. Change
  3. To
  4. Convert

Answer: C) To

Explanation:

The to keyword is used to explicitly transform data from one type to another.

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41. Which of the following type of delays are used to simulate how digital circuits respond to changes in input signals?

  1. Transport delays
  2. Time delay
  3. Inertial delay
  4. Signal delay

Answer: C) Inertial delay

Explanation:

Inertial delays are used to simulate how digital circuits respond to changes in input signals.

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42. In the VHDL code, inertial delays are commonly expressed with the ____ keyword.

  1. Before
  2. After
  3. Inertial
  4. Inertia
  5. Time

Answer: B) After

Explanation:

In VHDL code, inertial delays are commonly expressed with the after keyword.

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43. ____ delays are employed in circuits to simulate the temporal behavior of continuous signals or occurrences.

  1. Transport delays
  2. Time delay
  3. Inertial delay
  4. Signal delay

Answer: A) Transport delays

Explanation:

Transport delays are employed in circuits to simulate the temporal behavior of continuous signals or occurrences.

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44. In VHDL code, the ____ keyword is used to specify transport delays.

  1. Wait
  2. End
  3. Finish
  4. Delay

Answer: D) Delay

Explanation:

In the VHDL code, the delay keyword is used to specify transport delays.

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45. Rise delay and fall delay are the types of which kind of delays?

  1. Inertial delay
  2. Transport delay

Answer: A) Inertial delay

Explanation:

Rise delay and fall delay come under inertial delay.

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46. Multiple generics can be declared within an entity?

  1. True
  2. False

Answer: A) True

Explanation:

True, multiple generics can be declared within an entity.

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47. In the entity instantiation statement, which of the following clause is used to associate generic names with the appropriate values?

  1. Port map
  2. Generic map
  3. Generic entity
  4. Entity map

Answer: B) Generic map

Explanation:

In the entity instantiation statement, the 'generic map' clause is used to associate generic names with the appropriate values.

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48. Which of the following statement is used to aggregate a collection of concurrent or sequential statements into a single block?

  1. Block statement
  2. Concurrent statement

Answer: A) Block statement

Explanation:

The block statement is used to aggregate a collection of concurrent or sequential statements into a single block, hence establishing a hierarchical structure within the design.

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49. In the block statement, Signals and variables specified outside the block can be directly accessed within the block?

  1. True
  2. False

Answer: B) False

Explanation:

Signals and variables specified outside the block cannot be directly accessed within the block.

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50. Concurrent statement can directly interact with signals specified outside of their process or block scope?

  1. True
  2. False

Answer: A) True

Explanation:

Concurrent statements can directly interact with signals specified outside of their process or block scope.

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51. The signal assignment statement is a ____ statement

  1. Concurrent
  2. Sequential
  3. Block

Answer: A) Concurrent

Explanation:

The signal assignment statement is concurrent.

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52. ____ have a local scope and are only accessible within the process or block where they are defined.

  1. Signals
  2. Variables
  3. Both

Answer: B) Variables

Explanation:

Variables have a local scope and are only accessible within the process or block where they are defined.

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53. The package body contains ____.

  1. The implementation details for the functions
  2. Procedures specified in the package
  3. Both
  4. None

Answer: C) Both

Explanation:

The package body contains the implementation details for the functions and procedures specified in the package.

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54. Packages have which kind of scope?

  1. Local scope
  2. Global scope

Answer: B) Global scope

Explanation:

Packages have a global scope, which means they can be used and accessible from anywhere in the design.

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55. Which of the following is the correct syntax for using an attribute in VHDL?

  1. Attribite.element.attribute_name
  2. Attribute-global-element.attribute_name
  3. Global_element.attribute_name
  4. element.attribute_name

Answer: D) element.attribute_name

Explanation:

The syntax for using an attribute is: element.attribute_name.

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56. The public declarations and definitions that are available outside of the package are contained in the ____.

  1. Package body
  2. Package configuration
  3. Package declaration

Answer: C) Package declaration

Explanation:

The public declarations and definitions that are available outside of the package are contained in the package declaration.

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57. Variables are assigned using which of the following?

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

Answer: D) :<

Explanation:

Variables are assigned using variable assignment statements (:<) and are immediately updated inside the scope of the current scope.

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58. An entity can have multiple architectures?

  1. True
  2. False

Answer: A) True

Explanation:

An entity can have multiple architectures.

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59. In VHDL, function declarations, which of the following keyword specifies that the function has no side effects and depends only on the input arguments?

  1. Guarded
  2. Pure
  3. Impure
  4. Transport

Answer: B) Pure

Explanation:

In function declarations, Pure specifies that the function has no side effects and depends only on the input arguments.

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60. Entities or packages from a specified library are imported for usage in the current design by utilizing which of the following keyword?

  1. Load
  2. Add
  3. Copied
  4. Use

Answer: D) Use

Explanation:

Entities or packages from a specified library are imported for usage in the current design by utilizing Use keyword.

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