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
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
1AB = 00, CD = 00
2AB = 00, CD = 01
3AB = 00, CD = 11
4AB = 00, CD = 10
5AB = 01, CD = 00
6AB = 01, CD = 01
7AB = 01, CD = 11
8AB = 01, CD = 10
9AB = 11, CD = 00
10AB = 11, CD = 01
11AB = 11, CD = 11
12AB = 11, CD = 10
13AB = 10, CD = 00
14AB = 10, CD = 01
15AB = 10, CD = 11
16AB = 10, CD = 10
2.Easy
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
1N1
2G1
3G2
3.Medium
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
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)
1AB = 00, CD = 00
2AB = 00, CD = 01
3AB = 00, CD = 11
4AB = 00, CD = 10
5AB = 01, CD = 00
6AB = 01, CD = 01
7AB = 01, CD = 11
8AB = 01, CD = 10
9AB = 11, CD = 00
10AB = 11, CD = 01
11AB = 11, CD = 11
12AB = 11, CD = 10
13AB = 10, CD = 00
14AB = 10, CD = 01
15AB = 10, CD = 11
16AB = 10, CD = 10
5.Hard
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
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. AB = 01, CD = 10
2. N1
3. N = 4
4. AB = 01, CD = 01
5. Q = 3
6. Q = 2
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