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 m9 (variables A, B, C, D with A the most significant bit).
m9
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
NAND and NOR are universal gates: any logic function can be built from one of them alone. What is the minimum number N of 2-input NOR gates needed to build the XNOR function shown?
F = (A ⊕ B)′
N =
3.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(1, 2, 6, 7, 10)
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
4.Medium
Use the Karnaugh map to find the minimal sum-of-products (SOP) form of F(A, B, C, D) = Σm(2, 3, 4, 5, 7, 14). How many product terms N does it have?
F(A, B, C, D) = Σm(2, 3, 4, 5, 7, 14)
N =
5.Hard
Find the minimal SOP form of F(A, B, C, D) = Σm(4, 10, 13, 14) + d(9, 11), where d marks the don't-care conditions. How many literals L does it contain?
F(A, B, C, D) = Σm(4, 10, 13, 14) + d(9, 11)
L =
6.Hard
A 4-bit ring counter Q₃Q₂Q₁Q₀ starts at 1100. At every clock edge the bits shift one place to the right (Q₃ → Q₂ → Q₁ → Q₀) and Q₃ receives Q₀. Give the state Q = Q₃Q₂Q₁Q₀ as a decimal number after 10 clock edges.
Q₃Q₂Q₁Q₀ = 110010
Q =
Answer key
1. AB = 10, CD = 01
2. N = 4
3. AB = 00, CD = 01
4. N = 4
5. L = 10
6. Q = 3
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