This set of Logic Design Multiple Choice Questions & Answers (MCQs) focuses on “A Sequential Parity Checker”.
1. What is the main purpose of a parity bit?
a) Maintain odd number of 1s in a bit stream
b) Maintain even number of 1s in a bit stream
c) Error detection
d) Increase the stream length
View Answer
Explanation: Parity bits are used to detect error in a data transmission system. Suppose a data is being transmitted in groups of 7 bits. If any odd parity system finds the number of 1s in a group as an even number, then the system will add an additional parity bit 1 at the end of the package to make the total number of 1s in the package odd. Otherwise, it will add a 0 bit at the end of the package. Thus, at the receiving end, an error can be detected if even number of 1s are found.
2. A digital communication system sends and receives 7-bit data packages. In which of the following cases a parity bit 1 will be needed if an even parity transmission system is used?
a) 0110010
b) 0110110
c) 1100110
d) 0010001
View Answer
Explanation: Only the data package 0110010 contains odd number of 1s. So, an even parity system will add a parity bit of 1 to avoid error when transmitting the package. Hence the right answer is 0110010.
3. Which flip flop is generally used to build a sequential even parity checker?
a) SR flip-flop
b) JK flip-flop
c) T flip-flop
d) Master Slave flip-flop
View Answer
Explanation: If we use a negative edge triggered T flip-flop with initial state 0, and pass the input data pack to the T input, then an even number of 1s will be needed to make the final output zero as the flip flop will toggle its output after each negative clock pulse as 1 → 0 → 1 → 0……… So, the output will only be 0 if the parity is even.
4. How many states are there in the state machine of a sequential parity checker?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: There are two cases those can be detected in a parity checker – Even parity or Odd parity. Hence, two states can be found in any sequential parity checker. The right answer is 2.
5. Which pair is the correct match for an odd parity transmission system?
a) Data = 1101 000 Parity = 1
b) Data = 1001 000 Parity = 0
c) Data = 1101 000 Parity = 0
d) Data = 1101 110 Parity = 1
View Answer
Explanation: Only the combination “1101000” and parity bit 0 combines together keeping an odd number of 1s in the final byte “11010000”. So that combination is the right combination for an odd parity transmission system.
6. Which sequential device must be used to build an odd parity checker?
a) Positive edge triggered JK flip-flop
b) Positive edge triggered T flip-flop
c) Negative edge triggered JK flip-flop
d) Negative edge triggered T flip-flop
View Answer
Explanation: If a negative edge triggered T flip-flop with initial state 0 is used, and if the input data pack is sent to the T input, then an even number of 1s will make the final output zero as the flip flop will toggle its output after each positive clock pulse between 0 and 1……… So odd number of 1s will give the output 1 which will detect an odd parity.
7. Which one of the following is not true?
a) Parity checking procedure can detect errors
b) Parity bits can be both 0 and 1
c) Only one parity bit is added after a data pack
d) Parity bit can only be 1 but not 0
View Answer
Explanation: Parity bits are used to detect error in a data transmission system. Based on the number of 1s in a data pack and based on the parity system, the last parity bit is added. Suppose a data is being transmitted in groups of 7 bits. If any odd parity system finds the number of 1s in a group as an even number, then the system will add an additional parity bit 1 at the end of the package to make the total number of 1s in the package odd. Otherwise, it will add a 0 bit at the end of the package.
8. What parity bit will be added to the following data pack after examined by an even parity checker?
100100101
a) 1
b) 0
c) Can’t be determined
d) No parity bit will be added
View Answer
Explanation: Parity bits are used to detect error in a data transmission system. Based on the number of 1s in a data pack and based on the parity system, the last parity bit is added. The data pack 100100101 has total 8 bits. So, the even parity system will add a 0-parity bit to keep the total number of 1s even in the pack.
9. What is the parity of the binary representation of -23 in an 8 bit system?
a) Even
b) Odd
c) Can’t be determined directly
d) Adequate data not given
View Answer
Explanation: Parity bits are used to detect error in a data transmission system. Based on the number of 1s in a data pack and based on the parity system, the last parity bit is added. The binary representation of 23 is 00010111. Thus by 2’s complement method, we get -23 as its 2’s complement. Hence, -23 is equivalent to binary 11101001 in an 8 bit system. This value has 5 1s in it. Thus, the parity is odd.
10. A sequential odd parity checker checked a data pack and added a 1 after it. Which one of the following data packs can be the possible one?
a) 111010
b) 010101
c) 111000
d) 100000
View Answer
Explanation: Parity bits are used to detect error in a data transmission system. Based on the number of 1s in a data pack and based on the parity system, the last parity bit is added. Here the first data pack alone consists of even number of 1s. So, the odd parity checker will add a 1 after it to make the number of 1s odd.
11. For which one of the following, sequential parity checker is useful?
a) Analog Communication
b) Digital Communication
c) Both analog or digital
d) In specific cases of digital communication
View Answer
Explanation: Parity bits are used to detect error in a data transmission system. Based on the number of 1s in a data pack and based on the parity system, the last parity bit is added. As we send bit streams in case of digital communication only thus, the answer will be digital communication.
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