Package declaration and body in VHDL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a package named My_Pkg.

VHDL

package [1] is
  constant WIDTH : integer := 8;
end package;

Drag options to blanks, or click blank then click option'

APkg_My

BMy_Pkg

CPackage1

DMyPackage

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different package name than declared.

Misspelling the package name.

The package name must match the declaration name exactly. Here, 'My_Pkg' is the correct package name.

2fill in blank

medium

Complete the code to start the package body for My_Pkg.

VHDL

package body [1] is
  -- package body implementation
end package body;

Drag options to blanks, or click blank then click option'

AMy_Pkg

BPkg_My

CPackage1

DMyPackage

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different name in the package body than in the declaration.

Omitting the package name in the body.

The package body must use the exact package name declared earlier, which is 'My_Pkg'.

3fill in blank

hard

Fix the error in the package declaration keyword.

VHDL

[1] My_Pkg is
  constant MAX_VAL : integer := 255;
end package;

Drag options to blanks, or click blank then click option'

Apackage body

Bpkg

Cpackage

Dpackage declare

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'package body' instead of 'package' for declaration.

Using invalid keywords like 'pkg' or 'package declare'.

The correct keyword to declare a package is 'package'. 'package body' is for the body, and others are invalid.

4fill in blank

hard

Fill both blanks to declare a constant and a function prototype inside the package.

VHDL

package My_Pkg is
  constant [1] : integer := 16;
  function [2] return integer;
end package;

Drag options to blanks, or click blank then click option'

ADATA_WIDTH

Bget_value

CMAX_SIZE

Dcalculate

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing constant and function names.

Using invalid identifiers.

The constant name is 'DATA_WIDTH' and the function prototype is 'get_value' as per common naming conventions.

5fill in blank

hard

Fill all three blanks to implement the function body returning the constant value.

VHDL

package body My_Pkg is
  function [1] return integer is
  begin
    return [2];
  end [3];
end package body;

Drag options to blanks, or click blank then click option'

Aget_value

BDATA_WIDTH

Dcalculate

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching function names in start and end.

Returning an undefined constant.

The function name is 'get_value', it returns the constant 'DATA_WIDTH', and the function ends with 'end get_value;'.

Practice

1. What is the main purpose of a package declaration in VHDL?

easy

A. To define the entity and architecture of a design

B. To list constants, types, and function headers available for reuse

C. To implement the internal logic of functions

D. To simulate the behavior of a circuit

Solution

1. Step 1: Understand the role of package declaration

   The package declaration specifies what items (constants, types, function headers) are available to other parts of the design.

2. Step 2: Differentiate from package body

   The package body contains the actual implementation of functions, not the declaration.

3. Final Answer:

   To list constants, types, and function headers available for reuse -> Option B

4. Quick Check:

   Package declaration = lists available items [OK]

Hint: Declaration lists items; body defines them [OK]

Common Mistakes:

• Confusing package declaration with package body
• Thinking package declaration implements functions
• Mixing entity/architecture with packages

2. Which of the following is the correct syntax to start a package declaration named MyPackage in VHDL?

easy

A. package MyPackage is

B. package body MyPackage is

C. entity MyPackage is

D. architecture MyPackage of package is

Solution

1. Step 1: Identify package declaration syntax

   The correct syntax to declare a package is package PackageName is.

2. Step 2: Eliminate other options

   package body is for the package body, entity and architecture are unrelated to package declaration.

3. Final Answer:

   package MyPackage is -> Option A

4. Quick Check:

   Package declaration starts with 'package Name is' [OK]

Hint: Package declaration starts with 'package Name is' [OK]

Common Mistakes:

• Using 'package body' instead of 'package' for declaration
• Confusing entity/architecture keywords with package
• Incorrect order of keywords

3. Given the following package declaration and body, what will be the output of TestFunc(3)?

package MathPkg is
  function TestFunc(x : integer) return integer;
end package MathPkg;

package body MathPkg is
  function TestFunc(x : integer) return integer is
  begin
    return x * x;
  end TestFunc;
end package body MathPkg;

medium

A. Compilation error

B. 3

C. 6

D. 9

Solution

1. Step 1: Understand function implementation in package body

   The function TestFunc returns the square of the input x (x * x).

2. Step 2: Calculate output for input 3

   Input 3 squared is 3 * 3 = 9.

3. Final Answer:

   9 -> Option D

4. Quick Check:

   3 squared = 9 [OK]

Hint: Function returns x squared; input 3 -> 9 [OK]

Common Mistakes:

• Confusing declaration with implementation
• Assuming function returns input unchanged
• Thinking package body is optional for function

4. Identify the error in the following VHDL package code:

package Utils is
  function Add(a : integer; b : integer) return integer;
end package Utils;

package body Utils is
  function Add(a : integer; b : integer) return integer is
  begin
    return a + b
  end Add;
end package body Utils;

medium

A. Missing semicolon after return statement in function body

B. Package declaration missing 'body' keyword

C. Function parameters must be declared in package body only

D. Package body cannot contain function implementations

Solution

1. Step 1: Check function body syntax

   The return statement return a + b is missing a semicolon at the end.

2. Step 2: Verify other parts

   Package declaration and body keywords are correct; parameters are correctly declared in both places; package body can contain function implementations.

3. Final Answer:

   Missing semicolon after return statement in function body -> Option A

4. Quick Check:

   Statements need semicolons in VHDL [OK]

Hint: Check semicolons after statements in function body [OK]

Common Mistakes:

• Omitting semicolon after return statement
• Confusing package declaration with package body syntax
• Thinking function parameters only go in body

5. You want to create a package that shares a constant array and a function that returns the sum of its elements. Which of the following correctly shows the package declaration and body structure?

hard

A. package DataPkg is
constant Arr : integer_array := (1, 2, 3);
function SumArray return integer;
end package DataPkg;

package body DataPkg is
function SumArray return integer is
begin
return 6;
end SumArray;
end package body DataPkg;

B. package body DataPkg is
constant Arr : integer_array := (1, 2, 3);
function SumArray(a : integer_array) return integer;
end package body DataPkg;

package DataPkg is
function SumArray(a : integer_array) return integer is
begin
return 0;
end SumArray;
end package DataPkg;

C. package DataPkg is
constant Arr : integer_array := (1, 2, 3);
function SumArray(a : integer_array) return integer;
end package DataPkg;

package body DataPkg is
function SumArray(a : integer_array) return integer is
variable total : integer := 0;
begin
for i in a'range loop
total := total + a(i);
end loop;
return total;
end SumArray;
end package body DataPkg;

D. package DataPkg is
constant Arr : integer_array := (1, 2, 3);
function SumArray(a : integer_array) return integer;
end package DataPkg;

package body DataPkg is
function SumArray(a : integer_array) return integer is
begin
return a(1) + a(2);
end SumArray;
end package body DataPkg;

Solution

1. Step 1: Package declaration

   The declaration must contain the constant array definition constant Arr : integer_array := (1, 2, 3); and the function prototype function SumArray(a : integer_array) return integer;. This allows reuse across designs.

2. Step 2: Package body

   The body implements the function with a loop to sum all elements: variable total : integer := 0; for i in a'range loop total := total + a(i); end loop; return total;. Distractors lack proper structure, parameters, or dynamic summation.

3. Final Answer:

   Correct structure: constant and prototype in declaration, dynamic sum loop in body -> Option C

4. Quick Check:

   Declaration lists; body defines function logic [OK]

Hint: Declaration lists constants and function headers; body implements functions [OK]

Common Mistakes:

• Swapping package and package body order
• Omitting function parameters in declaration
• Incorrect function implementation missing loop or summation