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 = 1N1N2G1G2G3F

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. 2N2
  3. 3G1
  4. 4G2
  5. 5G3
2.Easy
A = 0B = 1C = 1N1G1G2F

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

A = 0B = 1C = 1
  1. 1N1
  2. 2G1
  3. 3G2
3.Medium
MUXC′I0​0I1​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 = 0, I₂ = 1, I₃ = C′. For how many of the 8 combinations of A, B and C is the output F = 1? Find N.

I₀ = C′I₁ = 0I₂ = 1I₃ = C′
N =
4.Medium
ABCD000111100001111011111

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, 3, 5, 8, 9)
  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
CLKJK12345678

A positive-edge-triggered JK flip-flop starts with Q = 0 and receives the inputs shown at 8 rising clock edges. How many times N does Q change state?

Q₀ = 0JK
N =
6.Hard
DQ0​Q0​DQ1​Q1​DQ2​Q2​DQ3​Q3​CLKJOHNSON

A Johnson (twisted-ring) counter is made of 4 D flip-flops, with the inverted last output fed back to the first input, and starts at all zeros. How many different states N does it go through?

n = 4
N =

Answer key

  1. 1. G1
  2. 2. G2
  3. 3. N = 4
  4. 4. AB = 01, CD = 01
  5. 5. N = 3
  6. 6. N = 8

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