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Important Digital Logic and Design Short Questions

Chapter: 29
Question 1:
How is a frequency counter used to measure the frequency of an input signal?
Answer: A frequency counter measures the number of clock pulses within a predetermined time interval and calculates the frequency by dividing the count by the time interval.
Chapter: 29
Question 2:
What is the role of the active-low LOAD input in the 74HC190 counter?
Answer: The active-low LOAD input is used to load a preset 4-bit value into the counter, enabling the counter to start counting from a specific value.
Chapter: 29
Question 3:
Explain the function of the "D/U" pin on the 74HC190 counter IC.
Answer: The "D/U" pin determines the counting direction of the counter: logic 1 for counting down and logic 0 for counting up.
Chapter: 30
Question 4:
What happens at time interval t9 in the digital clock timing diagram?
Answer: At time interval t9, the units counter reaches 1001 (9), setting the RCO signal to logic 1, indicating the terminal count of the 74x160 decade counter. This activates the tens counter.
Chapter: 30
Question 5:
How does the RCO signal affect the tens counter in a digital clock?
Answer: The RCO signal, when set to logic 1, enables the tens counter by connecting to the ENP and ENT enable signals. It allows the tens counter to increment when the units counter recycles to 0000.
Chapter: 30
Question 6:
What occurs at interval t19 in the digital clock counter?
Answer: At interval t19, the units counter reaches its terminal count again, activating the RCO signal. This allows the tens counter to increment from 0001 to 0010.
Chapter: 30
Question 7:
What is the purpose of the 3-input AND gate in the timing sequence from t56 to t64?
Answer: The 3-input AND gate outputs logic high when the units counter reaches its terminal count at t59. This signal enables the next counter by connecting to the ENP and ENT inputs.
Chapter: 30
Question 8:
How is the tens counter cleared in the timing sequence from t56 to t64?
Answer: The output of the NAND gate is set to logic 0 when the tens counter increments, which asynchronously clears the tens counter to 0000.
Chapter: 30
Question 9:
Describe the function of the NOT gate in the hours unit counter circuit.
Answer: The NOT gate is connected to the clock input of the J-K flip-flop, allowing the negative-edge triggered J-K flip-flop to trigger on the transition of the units counter from 0000 to 1001.
Chapter: 30
Question 10:
What triggers the J-K flip-flop in the hours unit counter circuit?
Answer: The J-K flip-flop is triggered at interval t10 when the J input is set to logic 1 and the K input is at logic 0, causing the flip-flop output Q to set to logic 1.