ISRO2007-19

Question

Assume that each character code consists of $8$ bits. The number of characters that can be transmitted per second through a synchronous serial line at $2400$ baud rate, and with two stop bits is

• A. $109$
• B. $216$
• C. $218$
• D. $219$

Answer 1

Baud Rate =2400  

Serial port is capable of transferring a maximum of 2400 bits per second.

Transmission rate = 2400 bps

Here we are going to have 1 start bit, 2 stop bits  Total bits= 11 bits.

So, number of characters transmitted per second = 2400 / 11 = 218.18.

Take floor =218

Ref: https://gateoverflow.in/2287/gate1993-6-4-isro2008-14
(comments will help also)

Comments

http://techdifferences.com/difference-between-synchronous-and-asynchronous-transmission.html

Just read the link above.

Asynchronous	Synchronous
Synchronization using start and stop bits with a gap between bytes Slower. Less error prone Similar to sending a letter Used for unknown or low data rates. Before the start of transmission, clocks at both ends are to be synchronized. This is achieved by sending special character bytes called sync bytes or sync characters	sender and receiver use the same clock signal   More error prone Similar to phone call Transmission of a large block of data at relatively higher bit rates resynchronize at the start of each new character received using start and stop bits which should be in opposite polarity 1-0 Regrouping the bits into meaningful bytes is done by the receiver.

According to this, for a synchronous transmission, there is no need to add start and stop bits!!
Given Question asks about synchronous transmission. So calculation must be 2400/8 =300
Please correct me if I am wrong

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same thought here

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bro thats a typo :D its not             a synchronous                asynchronous  in the original question

Answer 2

Baud rate 2400

then bit rate 2400/2=1200

Here we have 2 stop bits and must have 1 start bits

Size of each character=(8+2+1)=11bits

Number of characters =1200/11 =109

Ans A)

Comments

@reena baud rate =2* bit rate  is simply one formula to remember

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@srestha i don't think it is always the case.it might be that there are 3 pulses per bit.then in this case baud rate=3*bit rate.

plz clarify..

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yes, might be.

U got some example of it?

Answer 3

Baud rate=2400

Baud rate=2*bit rate

http://www.pccompci.com/Baud_Rate.html

Bit rate=1200

1 start bit,2 stop bits total=11 bits

number of character transmitted per second=floor(1200/11)=109

option A

Comments

@ arjun sir

could you please check this

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http://electronicdesign.com/communications/what-s-difference-between-bit-rate-and-baud-rate

Answer 4

Synchronous communication requires that the clocks in the transmitting and receiving devices are synchronized – running at the same rate – so the receiver can sample the signal at the same time intervals used by the transmitter. No start or stop bits are required. For this reason “synchronous communication permits more information to be passed over a circuit per unit time.
2400 baud means that the serial port is capable of transferring a maximum of 2400 bits per second.
Number of 8-bit characters that can be transmitted per second = 2400/8 = 300