3.3. Hardware
A subsection of Computer Science, 9608, through 3. Advanced Theory
Listing 10 of 48 questions
The truth table for a logic circuit with four inputs is shown. INPUT OUTPUT P Q R S X Write the Boolean expression for the truth table as a sum-of-products. X = Complete the Karnaugh Map (K-map) for the truth table. PQ RS The K-map can be used to simplify the expression in part . Draw loops around appropriate groups of 1s in the table in part to produce an optimal sum-of-products. Write the simplified sum-of-products expression for your answer to part . X = Simplify your expression for X in part using Boolean algebra. Show your working.
9608_s21_qp_32
THEORY
2021
Paper 3, Variant 2
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A motor is controlled by a logic circuit. The circuit has inputs (0 or 1) from three sensors R, T and W. The motor is switched off when the output from the logic circuit is 1. The following table shows the three sensors and the conditions being monitored. Sensor Description Binary value Condition R rotation rotation = 4000 rpm T temperature temperature >= 90 °C temperature = 50 litre/min water flow rate = 90 °C and rotation >= 4000 rpm or temperature = 50 litre/min Draw a corresponding logic circuit. R T X W Give a logic statement corresponding to the logic circuit in part . Complete the truth table for this system. INPUT Workspace OUTPUT X R T W
9608_w16_qp_11
THEORY
2016
Paper 1, Variant 1
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A motor is controlled by a logic circuit. The circuit has inputs (0 or 1) from three sensors R, T and W. The motor is switched off when the output from the logic circuit is 1. The following table shows the three sensors and the conditions being monitored. Sensor Description Binary value Condition R rotation rotation = 4000 rpm T temperature temperature >= 90 °C temperature = 50 litre/min water flow rate = 90 °C and rotation >= 4000 rpm or temperature = 50 litre/min Draw a corresponding logic circuit. R T X W Give a logic statement corresponding to the logic circuit in part . Complete the truth table for this system. INPUT Workspace OUTPUT X R T W
9608_w16_qp_13
THEORY
2016
Paper 1, Variant 3
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Complete the truth table for this 2-input NAND gate: A B X A B X Complete the truth table for this 3-input NAND gate: A C B X A B C X A SR flip-flop is constructed using two NAND gates. S R Q Q Complete the truth table for the SR flip-flop: S R Q Q Initially R changed to 1 S changed to 0 S changed to 1 S and R changed to 0 The final row in the table in part bshows that the output for both Q and Q is 1. Explain why this is a problem. Another type of flip-flop is the JK flip-flop. A JK flip-flop is constructed as follows: J Clock K Q Q Complete this truth table for the JK flip-flop. Working space Initial values Final values J K Clock Q Q Q Q Explain why the JK flip-flop is an improvement on the SR flip-flop. Explain the role of flip-flops in a computer.
9608_w17_qp_31
THEORY
2017
Paper 3, Variant 1
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Complete the truth table for this NOR gate: A B X A B X A SR flip-flop is constructed using two NOR gates. R Q S Q Complete the truth table for the SR flip-flop: S R Q Q Initially S changed to 0 R changed to 1 R changed to 0 S and R changed to 1 Another type of flip-flop is the JK flip-flop. The JK flip-flop is an improvement on the SR flip-flop. The JK flip-flop has three inputs. Two of the inputs are the Set (J) and the Reset (K). State the third input. There are two problems with the SR flip-flop that the JK flip-flop overcomes. State each problem and state why it does not occur for the JK flip-flop. Problem 1 Problem 2
9608_w17_qp_32
THEORY
2017
Paper 3, Variant 2
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Complete the truth table for this 2-input NAND gate: A B X A B X Complete the truth table for this 3-input NAND gate: A C B X A B C X A SR flip-flop is constructed using two NAND gates. S R Q Q Complete the truth table for the SR flip-flop: S R Q Q Initially R changed to 1 S changed to 0 S changed to 1 S and R changed to 0 The final row in the table in part bshows that the output for both Q and Q is 1. Explain why this is a problem. Another type of flip-flop is the JK flip-flop. A JK flip-flop is constructed as follows: J Clock K Q Q Complete this truth table for the JK flip-flop. Working space Initial values Final values J K Clock Q Q Q Q Explain why the JK flip-flop is an improvement on the SR flip-flop. Explain the role of flip-flops in a computer.
9608_w17_qp_33
THEORY
2017
Paper 3, Variant 3
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A Boolean expression corresponds to the following truth table. INPUT OUTPUT A B C X Write the Boolean expression for the truth table by applying the sum‑of‑products. X = Complete the Karnaugh Map (K‑map) for the truth table. AB C The K‑map can be used to simplify the expression in part . Draw looparound appropriate groups of 1s in the table in part to produce an optimal sum‑of‑products. Write the simplified sum‑of‑products expression for your answer to part . X = A logic circuit with four inputs produces the following truth table. INPUT OUTPUT A B C D X Complete the K‑map that corresponds to the truth table. AB CD Draw looparound appropriate groups of 1s in the table in part to produce an optimal sum‑of‑products. Write the simplified sum‑of‑products expression for your answer to part . X =
9608_w18_qp_31
THEORY
2018
Paper 3, Variant 1
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Questions Discovered
48