What do you mean by synchronous and asynchronous transmission? Explain with figure.

Synchronous Transmission:   The type of transmission where data are sent block (frame) by block without any regular interval is called synchronous transmission.

8 bit flag

Control field

Data Field

Control field

8 bit  flag

                   Figure: Character format of synchronous transmission.

The block may be many bits in length to prevent timing drift between transmitter and receiver there clock has to be synchronized.. That’s why Manchester or differential Manchester encoding technique are used here.

Features:

            (i) Data are sent block by block.

            (ii) Data has to be sent after a specific time period.

            (iii) The interval between to sending block is equal.

            (iv) There is no start or stop bit.

            (v) a primary storage is needed to store the sending data.

(vi) It is more expensive.

(vii) It is more efficient.

Asynchronous Transmission:  This type of transmission ehere data are sent character by character without transmission.

Stop bit

Stop  bit

                                  Fig: Character format of asynchronous Transmission.

The strategy of type of transmission is to avoid the timing problem but not sending long uninterrupted series of data.

Features:

            (i) Data are sent character by character.

(ii) Data can be sent any time.

(iii) The time interval between to sending character is not equal.

(iv) There exists a start  and stop bit before and after every character.

(v) No primary storage is needed here.

(vi) It is less expensive.

            (vii) It is less efficient.