Synchronous & Asynchronous

Dear friend！
Asynchronous transmission (ATM) is a transmission mode in which each character is formed into a frame for transmission. A continuous character string is encapsulated into a continuous independent frame for transmission. The spacing between the characters can be arbitrary. Therefore, this transmission mode is called asynchronous transmission.
Asynchronous Transfer Mode (ATM) is a cell switching and multiplexing technology. ATM uses cells as transmission units. A cell has a fixed length of 53 bytes. The first 5 bytes are headers and the remaining 48 bytes are data segments. The header contains information such as the logical address, priority, header error control, and flow control of the cell. The data segment is loaded with user information or other management information of various services that are split into data blocks and transparently traverses the network.
In synchronous transmission mode, data blocks are used as the transmission unit. A special character or bit sequence must be attached to the head and tail of each data block to mark the start and end of a data block. Generally, a check sequence (such as a 16-bit or 32-bit CRC code) must be attached to the head and tail of each data block to implement error control on the data block. Synchronous transmission means that the time interval between data blocks is fixed, and the time relationship between data blocks must be strictly specified.

The biggest difference between them is:

Synchronous transmission is to notify the recipient that the message has arrived.

Asynchronous transmission means that the recipient does not know when the message will be delivered.

Thanks！

Dear User,

Asynchronous Transmission:

- It uses the start and stop bits for signifying the beginning bit of ASCII character that is to be transmitted.

- For instance, ‘0100 0001 would become ‘1 0100 0001 000 1 0’’.

- The additional one bit at the beginning and ending of the transmission refers the receiver that a character is entering and the character is ended.

- When data need to be sent intermittently, this method is used.

- The start and stop bits are supposed to be opposite polarity.

- By this process, the receiver recognizes the second packet of the information that is being sent.

Synchronous Transmission:

- Synchronous transmission does not use start and stop bits, hence data transfer rate is quicker.

- The transmission is synchronized by speeding up at both the sending and receiving ends.

- This uses clock signals that are built at each component.

- Continual stream of data is sent between two nodes.

- Re-synchronization is one of the methods to address the lost bits.

- This method uses check digits instead of parity bits for ensuring the byte is correctly being interpreted and received.

Thanks!