# Digital Circuits Questions and Answers – Propagation Delay in Ripple Counter

This set of Digital Electronics/Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Propagation Delay in Ripple Counter”.

1. Modulus refers to ____________
a) A method used to fabricate decade counter units
b) The modulus of elasticity, or the ability of a circuit to be stretched from one mode to another
c) An input on a counter that is used to set the counter state, such as UP/DOWN
d) The maximum number of states in a counter sequence

Explanation: Modulus is defined as the maximum number of stages/states a counter has. It is independent of the number of states the counter will actually traverse.

2. A sequential circuit design is used to ____________
a) Count up
b) Count down
c) Decode an end count
d) Count in a random order

Explanation: A sequential circuit design is used to count in a random manner which is faster than the combinational circuit. It is used for storing data.

3. In general, when using a scope to troubleshoot digital systems, the instrument should be triggered by ____________
a) The A channel or channel 1
b) The vertical input mode, when using more than one channel
c) The system clock
d) Line sync, in order to observe troublesome power line glitches

Explanation: All the information is sent from one end to another end through the clock pulse which behaves like a carrier. So, for troubleshooting it should be triggered by the same. Since the system clock is internally produced.

4. Which counters are often used whenever pulses are to be counted and the results displayed in decimal?
a) Synchronous
b) Bean
d) BCD

Explanation: BCD means Binary Coded Decimal, which means that decimal numbers coded of binary numbers. It displays the decimal equivalent of corresponding binary numbers.

5. The ________ counter in the Altera library has controls that allow it to count up or down, and perform synchronous parallel load and asynchronous cascading.
a) 74134
b) LPM
c) Synchronous
d) AHDL

Explanation: The library of parameterized modules (LPM) counter in the Altera library has controls that allow it to count up or down, and perform synchronous parallel load and asynchronous cascading.

6. The minimum number of flip-flops that can be used to construct a modulus-5 counter is ____________
a) 3
b) 8
c) 5
d) 10

Explanation: The minimum number of flip-flops used in a counter is given by: 2(n-1)<=N<=2n.
Thus, for modulus-5 counter: 22 <= N <= 23, where N = 5 and n = 3.

7. The duty cycle of the most significant bit from a 4-bit (0–9) BCD counter is ____________
a) 20%
b) 50%
c) 10%
d) 80%

Explanation: There are 10 states, out of which MSB is high only for (1000, 1001) 2 times. Hence duty cycle is 2/10*100 = 20%. Since the duty cycle is the ratio of on-time to the total time.

8. Normally, the synchronous counter is designed using ____________
a) S-R flip-flops
b) J-K flip-flops
c) D flip-flops
d) T flip-flops

Explanation: Since J-K flip-flops have options of recovery from toggle condition and by using less number of J-K flip-flops a synchronous counter can be designed. So, it is more preferred. Also, because JK-flip-flops resolves the problem of Forbidden States.

9. MOD-16 counter requires ________ no. of states.
a) 8
b) 4
c) 16
d) 32

Explanation: 2n >= N >= 2(n-1), by using this formula we get the value of N=16 for n=4.

10. What is a state diagram?
a) It provides the graphical representation of states
b) It provides exactly the same information as the state table
c) It is same as the truth table
d) It is similar to the characteristic equation

Explanation: The state diagram provides exactly the same information as the state table and is obtained directly from the state table.

11. High speed counter is ____________
a) Ring counter
b) Ripple counter
c) Synchronous counter
d) Asynchronous counter

Explanation: Synchronous counter doesn’t have propagation delay. Propagation delay refers to the amount of time taken in producing the output when the input is altered.

12. Program counter in a digital computer ____________
a) Counts the number of programs run in the machine
b) Counts the number of times a subroutine
c) Counts the number of time the loops are executed
d) Points the memory address of the current or the next instruction

Explanation: Program counter in a digital computer points the memory address of the current or the next instruction which is to be executed.

13. Fundamental mode is another name for ____________
a) Level operation
b) Pulse operation
c) Clock operation
d) Edge operation

Explanation: Whatever the input given to the devices are in the form of pulses always. That is why it is known as a fundamental mode.

Sanfoundry Global Education & Learning Series – Digital Circuits.

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