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Synchronous vs Asynchronous Communication: 4 talking points

Embedded systems are the heart of many products and intelligent devices these days. They play a crucial role in the efficient functioning of cars, domestic appliances, medical instruments and scientific equipment. Embedded devices communicate with each other to perform the tasks at hand. These devices interact and exchange information with other devices using a connected network for completing the tasks. This sharing of data is known as communication.

There are two types of communications in the computer and embedded systems networking — synchronous and asynchronous.

Whether a process runs synchronously is a primary factor in determining the device’s processing, networking, and fundamental qualities. Here we’ve listed the principal differences between synchronous and asynchronous communication.

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How do Synchronous and Asynchronous communication work?

Every device communicates efficiently by transmitting the data securely and sequentially. To communicate effectively, designers focus on implementing the right approach for exchanging data between the devices to achieve the desired output through minimal processing cost.

Embedded systems designers have recognised two methods of data communication between devices based on expected processing results. But before diving into the key differences between these two communication methods, let us understand the two terms separately.

Synchronous Communication

In the synchronous data transmission method, a continuous stream of data in the form of blocks or frames transmits over a clocked input. In this method, the sender and receiver synchronise through the clock frequency signals to ensure that the data received is in sequential order.

Synchronisation becomes necessary as there should be no gap between the data transfer, and hence the receiver should know from where the new block or frame starts.

Synchronous vs Asynchronous Communication: 4 talking points

This method is more reliable and efficient for sharing a large amount of data. Also, it helps to provide real-time communication between devices. Therefore, this method operates in a full-duplex data flow mode.

Smart appliances, home security systems and chat, telephonic and video calling services are some of the services that use synchronous communication techniques.


Asynchronous Communication

Well, in the asynchronous communication method, clock frequency signals are not used for synchronisation between sender and receiver. Here, a continuous stream of data passes in the byte format with a preceding start bit and ending stop bit.

During asynchronous communication, one character transmits at a time, where the size of each character is equivalent to eight bits. Also, two parity bits – a start bit & an end bit, append with these eight bits. Thus, a total of ten bits are transmitted to convey a character. Using the parity bits, the receiver can identify each character uniquely.

Synchronous vs Asynchronous Communication: 4 talking points

This is a half-duplex mode of communication that uses the control flow method. This mode of communication is rather simple, fast, economical and does not require two-way communication. It is a more reliable approach for sharing a small amount of data.

File transfers, emailing, and walkie-talkies are some examples where an asynchronous mode of communication works.

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Synchronous vs Asynchronous mode

While both these modes of communication have their respective roles when operating on a device or a service, it is good to know the fundamental differences between the two. These differences do emphasise the functioning of a system, but it also helps you understand how the system interacts and operates effectively.

Let’s reason out some basic but important differences between synchronous and asynchronous communication based on comparative parameters, and reason out the benefits and drawbacks of a device or application.

Data Transfer

As stated above already, this is the principal difference between the two methods of communication. In synchronous transmission, data travels in the form of blocks or frames per clock cycle. On the other hand, one-byte transfers at a time in asynchronous communication. Due to this difference, the medium of exchange and its performance largely varies.

Where some applications prompt you with instant messaging services, others give you the liberty to respond at your convenience. A chatbot and a support helpline are the best examples to contrast the differences between synchronous and asynchronous communication.

Speed

The synchronous mode is faster than the asynchronous mode of communication because it allows data sharing over a continuous clock cycle. As opposed to this, the asynchronous mode determines every character based on the parity bits, additional bits that the system validates.

Therefore, it is easier to identify the information conveyed based on blocks rather than the character bytes in the synchronous mode. For example, smartphone calling is quicker than talking over the walkie-talkie, as it allows both people to talk simultaneously. But a walkie-talkie will allow only one person to talk at a time, hence taking more time for information exchange.

Efficiency

The asynchronous transmission mode is less efficient than the synchronous mode because there remain gaps on the line during character transmission. These empty slots on the transmission line, while transmitting the data, keep the bandwidth idle for some time. There is an efficient use of transmission lines in synchronous mode, as the data exchange is continuous over the available bandwidth.

An apt example to elaborate on is file sharing using Bluetooth compared with the Fibre Optic Network. Bluetooth is less preferred as compared with USB optical cables because it allows you to exchange a single file at a time. However, USB cables capacitate you to share more than one file without any intervention or gaps.


Clock Synchronisation

As the name suggests, in synchronous mode, the clocks tune precisely between the sender and the receiver at the same frequency to allow the fluid exchange of information bytes. But asynchronous transmission doesn’t require synchronisation between the clocks at the transmitter and receiver end, as the data bytes are determined using the parity bits.

Therefore, while it stands mandatory to sync the clocks at both the ends of a communication line during synchronous transmission, the same doesn’t apply to its counterpart. The transmitter and receiver can function independently at different clock frequencies in asynchronous mode.


More underlying differences

Furthermore, the below comparison table will give you more points to differentiate between the two modes of communication.

Synchronous CommunicationAsynchronous Communication
Users need to wait until the data has been sent to receive a response.This process runs independently without awaiting a response from the receiver.
Information transmission speed is high in the form of blocks.Information is transmitted character by a character which takes some time.
It is costly to establish.It is economical.
The transmission time interval is constant.The transmission time interval is random.
Local storage is not required at transmission ends.Local buffer storage is required at both ends to assemble data bytes.
This is implemented by both hardware and software.It is mostly implemented by hardware.
Offers a large amount of data transfer.Only a small amount of data can be transferred.
It offers real-time communication between devices.There is a delay in communication.

Both methods have their advantages and disadvantages. While synchronous mode provides faster transmission and forwards bulk data, it is rather costly to implement.

Likewise, the asynchronous transmission mode is more economical and simplistic, but requires additional bits for the transmission of data. Hence, both methods are suitable for data transmission, provided they satisfy the functional requirements.

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