GATE | GATE-CS-2004 | Question 22

How many 8-bit characters can be transmitted per second over a 9600 baud serial communication link using asynchronous mode of transmission with one start bit, eight data bits, two stop bits, and one parity bit ?
(A) 600
(B) 800
(C) 876
(D) 1200


Answer: (B)

Explanation:
Background required – Physical Layer in OSI Stack

In serial Communications, information is transferred in or out one bit at a time.
The baud rate specifies how fast data is sent over a serial line. It’s usually expressed in units of bits-per-second (bps). Each block (usually a byte) of data transmitted is actually sent in a packet or frame of bits. Frames are created by appending synchronization and parity bits to our data.

"9600 baud" means that the serial port is capable of transferring a 
maximum of 9600 bits per second.

Total Data To send = 1 bit(start) + 8 bits(char size) + 1 bit(Parity) + 2 bits(Stop) 

= 12 bits.

Number of 8-bit characters that can be transmitted per second  = 9600/12 = 800.

This explanation is contributed by Pranjul Ahuja.

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