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 = 0B = 0C = 1N1G1G2G3F

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

A = 0B = 0C = 1
  1. 1N1
  2. 2G1
  3. 3G2
  4. 4G3
2.Easy
BAF

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 OR function shown?

F = A + B
N =
3.Medium
ABCD000111100001111000011302141507161121131151140819011010

Use the Karnaugh map to find the minimal sum-of-products (SOP) form of F(A, B, C, D) = Σm(3, 4, 5, 6, 9, 12, 13, 14, 15). How many literals L does it contain in total (a primed variable counts as one literal)?

F(A, B, C, D) = Σm(3, 4, 5, 6, 9, 12, 13, 14, 15)
L =
4.Medium
MUXC′I0​1I1​0I2​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 = 1, I₂ = 0, I₃ = C′. For how many of the 8 combinations of A, B and C is the output F = 1? Find N.

I₀ = C′I₁ = 1I₂ = 0I₃ = C′
N =
5.Hard
ABCD0001111000011110X00113X2X415X716112X1311511408X9011X10

For F(A, B, C, D) = Σm(3, 5, 6, 12, 14, 15) + d(0, 2, 4, 7, 9, 10, 13), where d marks the don't-care conditions, find the number N of essential prime implicants.

F(A, B, C, D) = Σm(3, 5, 6, 12, 14, 15) + d(0, 2, 4, 7, 9, 10, 13)
N =
6.Hard
TQ0​Q0​TQ1​Q1​TQ2​Q2​TQ3​Q3​CLKMOD-12

A synchronous mod-12 counter counts 0, 1, …, 11 and then returns to 0. It starts at 6. Which count Q (in decimal) does it show after 23 clock pulses?

Q0 = 623N = 12
Q =

Answer key

  1. 1. G2
  2. 2. N = 2
  3. 3. L = 13
  4. 4. N = 4
  5. 5. N = 2
  6. 6. Q = 5

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