GATE CSE 1997 | Question: 2.3

Question

Purpose of a start bit in $\text{RS-232}$ serial communication protocol is:

• A. to synchronize receiver for receiving every byte
• B. to synchronize receiver for receiving a sequence of bytes
• C. a parity bit
• D. to synchronize receiver for receiving the last byte

Comments

you might get a doubt whether the communication is synchronous serial communication or asynchronous serial communication

answer is asynchronous serial communication because they mention that start bit is RS-232

but in case of synchronous serial communication there is no start bit and end bit

Answer 1

 The start bit is used to signal the beginning of a byte and the stop bit is used to signal the end of a Byte. 

If question ask in synchronous serial communication then we need to append start bit for Frame , but since here it is not given so we need to assume asynchronous serial . Hence A is answer

Reffer : 

1.  GATE2002-1.11

Comments

which part of kurose and ross covers this communication portion?
btw your answer is better than others :)

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Plz give the complete link .

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@Anu007  is asynchronous always by default?? 

Answer 2

A) Because $\text{RS-232}$ requires a start before each byte transmission for synchronization.

Comments

Why not B) ?

Answer 3

option A ...

http://www.best-microcontroller-projects.com/how-rs232-works.html

Comments

Check my answer