Priority encoder in VHDL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a 4-bit input vector named 'data'.

VHDL

signal data : std_logic_vector([1] downto 0);

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A3

B4

C7

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 4 as the highest index instead of 3.

Confusing the direction of the vector range.

The input vector 'data' is 4 bits wide, so the highest index is 3 (0 to 3).

2fill in blank

medium

Complete the code to assign the output 'pos' with the highest priority bit index when 'data' is not zero.

VHDL

if data /= "0000" then
    pos <= [1];
end if;

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A"11"

B"00"

C"01"

D"10"

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning the wrong binary value for the bit position.

Confusing the bit pattern with the index.

The output 'pos' should be assigned the binary index of the highest priority bit set. Here, "01" represents index 1.

3fill in blank

hard

Fix the error in the process sensitivity list to include all inputs.

VHDL

process([1])
begin
    -- priority encoder logic
end process;

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Adata

Bpos

Cclk

Dreset

Attempts:

3 left

💡 Hint

Common Mistakes

Including clock or reset signals unnecessarily.

Omitting the input signal 'data' from the sensitivity list.

The process sensitivity list must include 'data' because the output depends on changes in 'data'.

4fill in blank

hard

Fill both blanks to complete the priority encoder output assignment and default case.

VHDL

with data select
    pos <= [1] when "1000",
           [2] when others;

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A"11"

B"00"

C"10"

D"01"

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the binary values for the bit positions.

Not providing a default case for 'when others'.

When the highest bit (bit 3) is set, 'pos' is "11" (binary 3). For all other cases, default to "00".

5fill in blank

hard

Fill all three blanks to complete the priority encoder logic with multiple conditions.

VHDL

if data(3) = '1' then
    pos <= [1];
elsif data(2) = '1' then
    pos <= [2];
else
    pos <= [3];
end if;

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

A"11"

B"10"

C"00"

D"01"

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning incorrect binary values for bit positions.

Not covering all conditions properly.

The priority encoder checks bits from highest to lowest. If bit 3 is set, output "11" (3). Else if bit 2 is set, output "10" (2). Otherwise, output "00" (0).