Digital logic: gates, K-maps & flip-flops worksheet with answers

Free printable Digital logic: gates, K-maps & flip-flops worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
ABCD0001111000011110

Click the cell of the 4-variable Karnaugh map that belongs to minterm m6 (variables A, B, C, D with A the most significant bit).

m6
  1. 1AB = 00, CD = 00
  2. 2AB = 00, CD = 01
  3. 3AB = 00, CD = 11
  4. 4AB = 00, CD = 10
  5. 5AB = 01, CD = 00
  6. 6AB = 01, CD = 01
  7. 7AB = 01, CD = 11
  8. 8AB = 01, CD = 10
  9. 9AB = 11, CD = 00
  10. 10AB = 11, CD = 01
  11. 11AB = 11, CD = 11
  12. 12AB = 11, CD = 10
  13. 13AB = 10, CD = 00
  14. 14AB = 10, CD = 01
  15. 15AB = 10, CD = 11
  16. 16AB = 10, CD = 10
2.Easy
A = 1B = 0C = 0G1N1G2F

The inputs of the logic circuit are A = 1, B = 0 and C = 0. Exactly one of its gates has the output 0. Click that gate.

A = 1B = 0C = 0
  1. 1N1
  2. 2G1
  3. 3G2
3.Medium
ABCD000111100001111010110302140517161121130151141809011010

Use the Karnaugh map to find the minimal product-of-sums (POS) form of F(A, B, C, D) = Σm(0, 1, 4, 6, 7, 8, 12, 13, 14). How many sum terms (factors) N does it have?

F(A, B, C, D) = Σm(0, 1, 4, 6, 7, 8, 12, 13, 14)
N =
4.Medium
ABCD000111100001111011111111

In this Karnaugh map exactly one 1 has no neighbouring 1, so it stays a group of one cell (a full minterm of four literals) in the minimal SOP form. Neighbours across the map edges count. Click that cell.

F = Σm(2, 5, 6, 10, 11, 12, 14, 15)
  1. 1AB = 00, CD = 00
  2. 2AB = 00, CD = 01
  3. 3AB = 00, CD = 11
  4. 4AB = 00, CD = 10
  5. 5AB = 01, CD = 00
  6. 6AB = 01, CD = 01
  7. 7AB = 01, CD = 11
  8. 8AB = 01, CD = 10
  9. 9AB = 11, CD = 00
  10. 10AB = 11, CD = 01
  11. 11AB = 11, CD = 11
  12. 12AB = 11, CD = 10
  13. 13AB = 10, CD = 00
  14. 14AB = 10, CD = 01
  15. 15AB = 10, CD = 11
  16. 16AB = 10, CD = 10
5.Hard
DQ3​Q3​DQ2​Q2​DQ1​Q1​DQ0​Q0​CLKJOHNSON

A 4-bit Johnson counter Q₃Q₂Q₁Q₀ starts at 0000. At every clock edge the bits shift one place to the right (Q₃ → Q₂ → Q₁ → Q₀) and Q₃ receives the inverse of Q₀. Give the state Q = Q₃Q₂Q₁Q₀ as a decimal number after 6 clock edges.

Q₃Q₂Q₁Q₀ = 00006
Q =
6.Hard
TQ0​Q0​TQ1​Q1​TQ2​Q2​CLKUP

A 3-bit binary up counter starts at 5 (decimal, Q = 101). Which count Q (in decimal) does it show after 21 clock pulses?

Q0 = 521n = 3
Q =

Answer key

  1. 1. AB = 01, CD = 10
  2. 2. N1
  3. 3. N = 4
  4. 4. AB = 01, CD = 01
  5. 5. Q = 3
  6. 6. Q = 2

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