Asynchronous vs. Synchronous Communication: Key Differences

This page describes the difference between asynchronous and synchronous communication.

Asynchronous Communication

In asynchronous communication, each data word is accompanied by a start bit at the beginning of the transmission and a stop bit at the end. Each binary code word represents one character. Low-speed data communications of up to 115 Kbaud are possible with asynchronous communication.

It is often considered reliable due to the presence of start and stop bits, which help in error detection. However, these start and stop bits effectively slow down the data transmission.

Synchronous Communication

In synchronous communication, data words are transmitted one after the other without the use of start and stop bits for each word.

For synchronization purposes, a group of synchronization (SYN) bits (a unique pattern of bits) is placed at the beginning, and a special code (e.g., ETX - End of Text) signaling is placed at the end of the block. SYN bits are typically 8 bits each.

Here, each block represents hundreds or even thousands of characters. The ETX code helps the receiving equipment identify the end of the block transmission. Although SYN and ETX are added along with the data to be transmitted, their overhead is less compared to the start and stop bits used in asynchronous transmission.

Therefore, synchronous communication offers a faster way of data communication compared to asynchronous communication.

The following table summarizes the key differences between asynchronous and synchronous communication: