Digital Principles And System Design Set 9

Computer Science Engineering (CSE)

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This set of Digital Principles and System Design Multiple Choice Questions & Answers (MCQs) focuses on Digital Principles And System Design Set 9

Q1 | The inputs of SR latch are                        
  • x and y
  • a and b
  • s and r
  • j and k
Answer: s and r
Explaination:
sr or set-reset latch is the simplest type of bistable multivibrator having two stable states. the inputs of sr latch are s and r while outputs are q
Q2 | When a high is applied to the Set line of an SR latch, then                        
  • q output goes high
  • q’ output goes high
  • q output goes low
  • both q and q’ go high
Answer: q output goes high
Explaination:
s input of a sr latch is directly connected to the output q. so, when a high is applied q output goes high and q’ low.
Q3 | When both inputs of SR latches are low, the latch
  • q output goes high
  • q’ output goes high
  • it remains in its previously set or reset state
  • it goes to its next set or reset state
Answer: it remains in its previously set or reset state
Explaination:
when both inputs of sr latches are low, the latch remains in it’s present state. there is no change in the output.
Q4 | When both inputs of SR latches are high, the latch goes                        
  • unstable
  • stable
  • metastable
  • bistable
Answer: metastable
Explaination:
when both gates are identical and this is “metastable”, and the device will be in an undefined state for an indefinite period.
Q5 | The register is a type of                        
  • sequential circuit
  • combinational circuit
  • cpu
  • latches
Answer: sequential circuit
Explaination:
register’s output depends on the past and present states of the inputs. the device which follows these properties is termed as a sequential circuit. whereas, combinational circuits only depend on the present values of inputs.
Q6 | How many types of registers are?
  • 2
  • 3
  • 4
  • 5
Answer: 4
Explaination:
there are 4 types of shift registers, viz., serial-in/serial-out, serial-in/parallel-out, parallel- in/serial-out and parallel-in/parallel-out.
Q7 | The main difference between a register and a counter is                        
  • a register has no specific sequence of states
  • a counter has no specific sequence of states
  • a register has capability to store one bit of information but counter has n-bit
  • a register counts data
Answer: a register has no specific sequence of states
Explaination:
the main difference between a register and a counter is that a register has no specific sequence of states except in certain specialised applications.
Q8 | In serial shifting method, data shifting occurs
  • universal shift register
  • unidirectional shift register
  • unipolar shift register
  • unique shift register
Answer: unidirectional shift register
Explaination:
the register capable of shifting in one direction is unidirectional shift register. the register capable of shifting in both directions is known as a bidirectional shift register.
Q9 | A register that is used to store binary information is called                        
  • data register
  • binary register
  • shift register
  • d – register
Answer: binary register
Explaination:
a register that is used to store binary information is called a binary register. a register in which data can be shifted is called shift register.
Q10 | A shift register is defined as                        
  • the register capable of shifting information to another register
  • the register capable of shifting information either to the right or to the left
  • the register capable of shifting information to the right only
  • the register capable of shifting information to the left only
Answer: the register capable of shifting information either to the right or to the left
Explaination:
the register capable of shifting information either to the right or to the left is termed as shift register. a register in which data can be shifted only in one direction is called unidirectional shift register, while if data can shifted in both directions, it is known as a bidirectional shift register.
Q11 | In digital logic, a counter is a device which
  • counts the number of outputs
  • stores the number of times a particular event or process has occurred
  • stores the number of times a clock pulse rises and falls
  • counts the number of inputs
Answer: stores the number of times a particular event or process has occurred
Explaination:
in digital logic and computing, a counter is a device which stores (and sometimes displays) the number of times a particular event or process has occurred, often in relationship to a clock signal.
Q12 | A counter circuit is usually constructed of
  • a number of latches connected in cascade form
  • a number of nand gates connected in cascade form
  • a number of flip-flops connected in cascade
  • a number of nor gates connected in cascade form
Answer: a number of flip-flops connected in cascade
Explaination:
a counter circuit is usually constructed of a number of flip-flops connected in cascade.
Q13 | 4 COUNTERS
  • 0 to 2n
  • 0 to 2n + 1
  • 0 to 2n – 1 d) 0 to 2n+1/2
Answer: 0 to 2n – 1 d) 0 to 2n+1/2
Explaination:
the maximum possible range of bit- count specifically in n-bit binary counter consisting of ‘n’ number of flip-flops is 0 to 2n-1. for say, there is a 2-bit counter, then it will count till 22-1 = 3. thus, it will count from 0 to 3.
Q14 | How many types of the counter are there?
  • 2
  • 3
  • 4
  • 5
Answer: 3
Explaination:
counters are of 3 types, namely, (i)asynchronous/synchronous, (ii)single and multi- mode & (iii)modulus counter. these further can be subdivided into ring counter, johnson counter, cascade counter, up/down counter and such like.
Q15 | A decimal counter has              states.
  • 5
  • 10
  • 15
  • 20
Answer: 10
Explaination:
decimal counter is also known as 10 stage counter. so, it has 10 states. it is also known as decade counter counting from 0 to 9.
Q16 | Ripple counters are also called                          
  • ssi counters
  • asynchronous counters
  • synchronous counters
  • vlsi counters
Answer: asynchronous counters
Explaination:
ripple counters are also called asynchronous counter. in asynchronous counters, only the first flip-flop is connected to an external clock while the rest of the flip-flops have their preceding
Q17 | Synchronous counter is a type of                          
  • ssi counters
  • lsi counters
  • msi counters
  • vlsi counters
Answer: msi counters
Explaination:
synchronous counter is a medium scale integrated (msi). in synchronous counters, the clock pulse is supplied to all the flip-flops simultaneously.
Q18 | Three decade counter would have                          
  • 2 bcd counters
  • 3 bcd counters
  • 4 bcd counters
  • 5 bcd counters
Answer: 3 bcd counters
Explaination:
three decade counter has 30 states and a bcd counter has 10 states. so, it would require 3 bcd counters. thus, a three decade counter will count from 0 to 29.
Q19 | BCD counter is also known as                          
  • parallel counter
  • decade counter
  • synchronous counter
  • vlsi counter
Answer: decade counter
Explaination:
bcd counter is also known as decade counter because both have the same number of stages and both count from 0 to 9.
Q20 | The parallel outputs of a counter circuit represent the                            
  • parallel data word
  • clock frequency
  • counter modulus
  • clock count
Answer: clock count
Explaination:
the parallel outputs of a counter circuit represent the clock count. a counter counts the number of times an event takes place in accordance to the clock pulse.
Q21 | A sequential logic can’t be executed by concurrent statements only.
  • true
  • false
Answer: true
Explaination:
it is true that a sequential logic can’t be executed by concurrent statements only. it requires the sequential statements because they make use of a clock signal.
Q22 | Which of the following sequential circuit doesn’t need a clock signal?
  • flip flop
  • asynchronous counter
  • shift register
  • latch
Answer: latch
Explaination:
latch has an enable input, but no clock signal. all other circuits including asynchronous counter needs a clock signal. it is called asynchronous because every flip flop doesn’t have same clock signal.
Q23 | The following timing diagram shows              flip flop.
  • t flip-flop
  • d flip-flop
  • sr flip-flop
  • jk flip-flop
Answer: d flip-flop
Explaination:
since there is only one input to the flip flop, therefore, it can be either d or t flip flop. but, the output becomes equal to the input signal as soon as there is a positive edge of the clock therefore, it is a delay flip flop.
Q24 | The process used for implementation of sequential logic in VHDL is called              process.
  • sequential process
  • combinational process
  • clocked process
  • unclocked process
Answer: clocked process
Explaination:
a process with a clock signal in its sensitivity list is called a clocked process. in case of sequential logic circuit, one needs a clock signal in the sensitivity list.
Q25 | Why do we need to define clock signal in the sensitivity list of the process?
  • to trigger the statement as soon as there is some event on clock
  • to trigger the clock signal as soon as there is some event on input
  • to trigger the clock signal as soon as there is some event on output
  • to trigger the statement as soon as there is some event on input
Answer: to trigger the statement as soon as there is some event on clock
Explaination:
to monitor the events on clock signal, whether it is positive triggered circuit or negative triggered circuit, we need to define the clock as a signal in the sensitivity list. when it is in the sensitivity list, then every single positive or negative edge of the signal will trigger the statements inside the process.
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