Browse Definitions :
Definition

USART (universal synchronous/asynchronous receiver/transmitter)

What is a USART (universal synchronous/asynchronous receiver/transmitter)?

A USART (universal synchronous/asynchronous receiver/transmitter) is hardware that enables a device to communicate using serial protocols. It can function in a slower asynchronous mode, like a universal asynchronous receiver/transmitter (UART), or in a faster synchronous mode with a clock signal. USARTs are no longer common in consumer PCs but are still used in industrial equipment and embedded systems.

USART vs. UART

A UART device can use asynchronous communication protocols. A USART device can use both asynchronous and synchronous communication protocols. Therefore, a USART can do anything a UART can do and more. Because a USART requires more complex circuitry and more communication lines to fully implement, many devices may only implement a UART to save on cost, complexity or power usage.

Asynchronous and synchronous serial communication

In serial communication, each bit of data is sent one at a time on a transmit wire. This is a serial communications interface. If the sender and the receiver don't agree on how the data is sent, such as the order and length of time of each bit, then the data becomes garbled, and they won't understand each other. Asynchronous and synchronous are two different ways to standardize how serial data is sent.

Asynchronous serial data

In asynchronous mode, only one data line is used to send data from the transmitter to the receiver. There is no shared synchronization signal from the sender to the receiver. So, the receiver has no way to know how fast or slow the data is coming. To circumvent this, both the sender and receiver must be manually configured beforehand to use the same data rate. A common shared baud rate is 9,600 bits per second.

Even sharing a common bit rate, it is possible for the devices to become slightly out of sync. Therefore, extra bits are added to each packet of data to ensure reliable transmission. A start and stop bit are almost always added to indicate each packet. Often, a parity bit is also added to indicate small errors. Adding these extra bits causes asynchronous communication to be less efficient.

The following are some example asynchronous serial protocols:

synchronous vs. asynchronous communication methods
Asynchronous and synchronous are two different ways to standardize how serial data is sent.


Synchronous serial data

In synchronous mode, a data and a clock line are used to send the data. The controller sends a clock signal, which synchronizes the controller and the peripheral at the same data rate. Because the clock signal keeps the devices in sync, the two devices don't need to be configured ahead of time to use the same bit rate.

Using a clock signal also removes the need to have extra start and stop bits. All the data can be sent continuously without pause. It also enables much faster bit rates as the sender doesn't need to worry about the receiver being able to keep up or get out of sync.

The following are some example synchronous protocols:

Current USART use

USARTs are no longer common for desktop computers, but they are still heavily used in industrial and embedded devices.

In the past, a USART was common in desktop PCs; it would control the serial port. The serial port would often be a DB9 connector on the rear of the computer. The serial port was used to connect to modems, mice and other peripherals. With the introduction of the much faster USB standard with autoconfiguration and plug and play, the serial port fell out of use. Most recent desktops no longer include a serial port.

A USART is still common in embedded and industrial systems, however. Many control systems still use serial communications to control equipment; programmable logic controllers; robotics; and heating, ventilation and air conditioning systems. A USART is also part of most microcontrollers to communicate with peripheral systems. Internet of things devices may have a USART to communicate with other devices.

See how CPU, GPU and DPU differ from one another, check out best practices for data center network optimization, explore the many components of modern storage infrastructure management and learn the differences between synchronous vs. asynchronous communications.

This was last updated in November 2022

Continue Reading About USART (universal synchronous/asynchronous receiver/transmitter)

Networking
  • network interface card (NIC)

    A network interface card (NIC) is a hardware component, typically a circuit board or chip, installed on a computer so it can ...

  • User Datagram Protocol (UDP)

    User Datagram Protocol (UDP) is a communications protocol primarily used to establish low-latency and loss-tolerating connections...

  • Telnet

    Telnet is a network protocol used to virtually access a computer and provide a two-way, collaborative and text-based ...

Security
  • advanced persistent threat (APT)

    An advanced persistent threat (APT) is a prolonged and targeted cyber attack in which an intruder gains access to a network and ...

  • Mitre ATT&CK framework

    The Mitre ATT&CK (pronounced miter attack) framework is a free, globally accessible knowledge base that describes the latest ...

  • timing attack

    A timing attack is a type of side-channel attack that exploits the amount of time a computer process runs to gain knowledge about...

CIO
HRSoftware
  • employee resource group (ERG)

    An employee resource group is a workplace club or more formally realized affinity group organized around a shared interest or ...

  • employee training and development

    Employee training and development is a set of activities and programs designed to enhance the knowledge, skills and abilities of ...

  • employee sentiment analysis

    Employee sentiment analysis is the use of natural language processing and other AI techniques to automatically analyze employee ...

Customer Experience
  • customer profiling

    Customer profiling is the detailed and systematic process of constructing a clear portrait of a company's ideal customer by ...

  • customer insight (consumer insight)

    Customer insight, also known as consumer insight, is the understanding and interpretation of customer data, behaviors and ...

  • buyer persona

    A buyer persona is a composite representation of a specific type of customer in a market segment.

Close