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
A = 1B = 1C = 1N1G1G2F

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

A = 1B = 1C = 1
  1. 1N1
  2. 2G1
  3. 3G2
2.Easy
ABCG1N1N2G2G3F

For the logic circuit shown, how many of the 8 combinations of the inputs A, B and C give the output F = 1? Find N.

A, B, C → F
N =
3.Medium
MUXCI0​C′I1​1I2​C′I3​ABS1​S0​F

A 4-to-1 multiplexer has its select inputs S₁ = A and S₀ = B, and its data inputs tied to I₀ = C, I₁ = C′, I₂ = 1, I₃ = C′. For how many of the 8 combinations of A, B and C is the output F = 1? Find N.

I₀ = CI₁ = C′I₂ = 1I₃ = C′
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(1, 2, 6, 7, 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
CLKJK123456

A positive-edge-triggered JK flip-flop starts with Q = 0 and receives the inputs shown. Click the first clock edge at which Q goes from 1 back to 0.

Q₀ = 0JK
  1. 1clock edge 1
  2. 2clock edge 2
  3. 3clock edge 3
  4. 4clock edge 4
  5. 5clock edge 5
  6. 6clock edge 6
6.Hard
ABCD000111100001111010X1130204151716112X130151140809111X10

For F(A, B, C, D) = Σm(0, 3, 5, 6, 7, 11, 12, 14) + d(1, 10, 13), where d marks the don't-care conditions, find the number N of essential prime implicants.

F(A, B, C, D) = Σm(0, 3, 5, 6, 7, 11, 12, 14) + d(1, 10, 13)
N =

Answer key

  1. 1. G1
  2. 2. N = 2
  3. 3. N = 5
  4. 4. AB = 00, CD = 01
  5. 5. clock edge 4
  6. 6. N = 1

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