What is the difference between synchronous and asynchronous data transmission?

Answer 1

Both of these forms of communication are a means of transmitting data. The difference is in the format that the data is transmitted.

Asynchronous communications is the method of communications most widely used for PC communication and is commonly used for e-mail applications, internet access, and asynchronous PC-to-PC communications. Through asynchronous communications, data is transmitted one byte at a time with each byte containing one start bit, eight data bits, and one stop bit, thus yielding a total of ten bits. With asynchronous communications, there is a high amount of overhead because every byte sent contains two extra bits (the start and stop bits) and therefore a substantial loss of performance.

Synchronous communications is the more efficient method of communications. CQ's connectivity solutions communicate through the synchronous method of communications.

Through synchronous communications, data is transmitted as frames of large data blocks rather than bulky individual bytes. One advantage of synchronous is that control information is easily inserted at the beginning and end of each block to ensure constant timing, or synchronization. Another advantage of synchronous is that it is more efficient than asynchronous. For example, a 56 Kbps dial-up synchronous line can carry 7000 bytes per second (56000/8) compared to a 56 Kbps dial-up asynchronous line which can only carry 5600 bytes per second (56000/10). When transmitting large amounts of information, this translates into a significant increase in speed and performance.

To see this work you can work out the efficiency rates and time that it takes to send each message

Asynchronous would be worked out as follows

To get the efficiency of it you

get assuming the message is being send over a 100mb line and 70 bytes to send and 300 characters

then it is

70*8 = 560 (the 8 is for the 8 bits to make up each byte)

the 70*2 (the start and stop bit) =140

= 700

then to

get 560*100/700= 80

that means that 80% efficient

To get the time

Asynchronous

300 *(1+7+1+1) =3000

take this and divide it by the size of the line in this case 100mb

so that is then

3000/100=30

that means that it would take 30 seconds to send

for

synchronous efficiency

Then

70*8= 560

then 4 bytes = 4*8 (the over head bits) = 32

560+32=592

560*100/592=94.5

then that's 94.5% efficient

and for the time then it is just

300+4*8=2342/100=23.42

that's then 23.42 seconds

this shows you which is faster and more efficient in each case

Answer 2

Sychronous transmission does not add start & stop bits at the beginning and end each byte transmitted for sending data segments while Asychronous transmission uses start & stop bits which are added at the start & end of data blocks.

Sychronous transmission provides 64 or 128 Kbps speed but

asychronous transmission provides 38.4 Kbps speed.

Answer 3

Synchronous Communication:

Data transfer method in which sent and received data flows at the same speed, and is spaced by timing signals.

In simple wording the clocks of source and destination are synchronized, from start of communication till the end.

Isosyncronous Communication:

communications system in which the source and target are each synchronized but each transmission contains a start bit and a stop bit.

Answer 4

• synchronous - the transmitter must send a separate clock signal to keep the receiver synchronized with it to successfully receive the data
• asynchronous - self synchronizing, the receiver is able to synchronize with the data as it is received without a separate clock signal also being sent from the transmitter to the receiver