What is the Difference Between Synchronous and Asynchronous Data Transfer? with Proper Definition and Brief Explanation

In synchronous data transfer, the transmitter and receiver are synchronized with the same clock pulse. In asynchronous data transfer, the transmitter and receiver do not use a common timing signal. That is the main difference between synchronous and asynchronous data transfer.

Data transfer is the process of sending data from the transmitter (sender) to the receiver. It can be synchronous or asynchronous. Synchronous data transfer uses synchronized clocks to transmit data. In contrast, asynchronous data transfer uses a flow control method to send start and stop bits with data.

Key areas covered

1. What is synchronous data transfer?
     – Definition, Functionality
2. What is asynchronous data transfer?
     – Definition, Functionality
3. What is the difference between synchronous and asynchronous data transfer?
     – Comparison of key differences

Key terms

Asynchronous data transfer, synchronous data transfer

What is synchronous data transfer?

In synchronous data transfer, the transmitter and receiver are synchronized and use a common timing signal. It uses timing signals for synchronization. Here, the data flows as a continuous stream one after the other. The transmitter sends data and the receiver counts the number of bits in the received data. Also, there are no gaps between the data. In this method, the time signals must be accurate to transfer data efficiently. Also, this method is faster than asynchronous data transfer.

                      Figure 1: Synchronous and Asynchronous Data Transfer

In a digital system, if the other registers share the same clock with the CPU registers, the data transfer between the CPU and the input and output devices is a synchronous data transfer. Both units take advantage of the common pulse generator clock.

What is asynchronous data transfer?

In asynchronous data transfer, the transmitter and receiver operate at different clock frequencies. It uses the start and stop bits to the data. According to the previous example (figure 1), each byte of data is embedded in the start and stop bits. The ‘0’ indicates the start bit while ‘1’ indicates the end bit. The ‘1’ and ‘0’ highlighted in red are the start and stop bits. Also, timing is not an important factor in asynchronous data transfer.

In a digital system, if the other registers and the CPU registers use their own private clocks, they have different timing signals. Therefore, the CPU and the input and output devices must coordinate to transfer data. It’s called asynchronous data transfer.

Difference between synchronous and asynchronous data transfer

Definition

Synchronous transfer is the data transfer method that sends a continuous stream of data to the receiver using regular timing signals that ensure that both the transmitter and the receiver are in sync with each other. Conversely, asynchronous data transfer is the data transfer method that sends data from the transmitter to the receiver with parity bits (start and stop bits) at uneven intervals. So this explains the fundamental difference between them.

Clocks

In synchronous data transfer, the sender and receiver operate at the same clock frequencies, while in asynchronous data transfer, the sender and receiver operate at different clock frequencies. So this is the main difference between synchronous and asynchronous data transfer.

Data transfer rate

Data transfer speed is another difference between synchronous and asynchronous data transfer. Synchronous transfer is faster than asynchronous transfer.

Start and stop bits

There is no overhead of additional start and stop bits in synchronous transfer. On the other hand, asynchronous data transfer uses start and stop bits.

Gaps between data

In synchronous data transfer, there are no gaps between the data and the data streams like a continuous stream. However, in asynchronous data transfer, there may be gaps between the data.

Timeslots

Synchronous transfer uses constant time intervals. In contrast, asynchronous transfer uses random or irregular time intervals. This is another difference between them.

Examples

For example, chat rooms and video conferencing use synchronous data transfer, while emails use asynchronous data transfer.

conclusion

The main difference between them is that in synchronous data transfer, the transmitter and receiver are synchronized with the same clock pulse, while in asynchronous data transfer, the transmitter and receiver do not use a common timing signal.

Reference:

1. Synchronous data transfer | COA, Educación 4u, December 11, 2017, Available here.
2. Asynchronus Data Transfer, Education 4u, April 17, 2018, Available here.

See More:

• System Architecture and Software Architecture