Synchronous and Asynchronous Data Transmission

Synchronous Transmission

Synchronous data transmission is a data transfer method in which a continuous stream of data signals is sent in the form of blocks or frames or chunks accompanied by timing signals.

Synchronization between the sender and the receiver is compulsory so that the source knows where the new byte begins, since there are no spaces included between the data.

In synchronous mode, the bits are sent successively with no separation between each character, so it becomes necessary to insert some synchronization elements with the message, this is called “Character-level Synchronization”.

For Example, if there are two bytes of data, say(10001101, 11001011) then it will be transmitted in the synchronous mode as follows:

Examples: Chatrooms, video conferencing, communication in CPU, etc.

Advantages

1. Synchronous transmission is more efficient and faster than asynchronous transmission.
2. Synchronous transmission is effective, dependable, and often utilised for transmitting a large amount of data.
3. Lower overhead and thus, greater throughput.

Disadvantages

1. Synchronous transmission is costly.
2. It is required that transmitter and receiver to be properly synchronized.

Asynchronous Transmission

Asynchronous Transmission is also known as start/stop transmission, sends data from the sender to the receiver in the form of byte or character using the flow control method.

Asynchronous transmission uses start and stop bits i.e., start and stop bits are added with data and does not use a clock to synchronize data between the source and destination.

In an asynchronous mode of communication, data bits can be sent at any point in time. The messages are sent at irregular intervals and only one data byte can be sent at a time. This type of transmission mode is best suited for short-distance data transfer.

For Example, if there are two bytes of data, say(10001101, 11001011) then it will be transmitted in the asynchronous mode as follows:

Examples: Emails, letters, data input from a keyboard to the computer. etc.

Advantages

1. Asynchronous transmission is straightforward and cost-effective.
2. Simple, doesn’t require synchronization of both communication sides.
3. Set-up is faster than other transmissions, so well suited for applications where messages are generated at irregular intervals.

Disadvantages

1. The data transmission can be slower due to the gaps present between different blocks of data.
2. Large relative overhead, a high proportion of the transmitted bits are uniquely for control purposes and thus carry no useful information.