astronomy

Universal synchronous and asynchronous receiver-transmitter

Universal synchronous and asynchronous receiver-transmitter is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Universal synchronous and asynchronous receiver-transmitter rather than just read about it. In short: A universal synchronous and asynchronous receiver-transmitter (USART, programmable communications interface or PCI) is a type of a serial interface device that can be programmed to communicate asynchronously or synchronously. See universal asynchronous receiver-transmitter (UART) for a discussion of the asynchronous capabilities of these devices.

Key takeaways

Universal synchronous and asynchronous receiver-transmitter belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Universal synchronous and asynchronous receiver-transmitter to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Universal synchronous and asynchronous receiver-transmitter from memory before moving on to harder problems.

Reference excerpt

A universal synchronous and asynchronous receiver-transmitter (USART, programmable communications interface or PCI) is a type of a serial interface device that can be programmed to communicate asynchronously or synchronously. See universal asynchronous receiver-transmitter (UART) for a discussion of the asynchronous capabilities of these devices.

Purpose and history The USART's synchronous capabilities were primarily intended to support synchronous protocols like IBM's synchronous transmit-receive (STR), binary synchronous communications (BSC), synchronous data link control (SDLC), and the ISO-standard high-level data link control (HDLC) synchronous link-layer protocols, which were used with synchronous voice-frequency modems. These protocols were designed to make the best use of bandwidth when modems were analog devices. In those times, the fastest asynchronous voice-band modem could achieve at most speeds of 300 bit/s using frequency-shift keying (FSK) modulation, while synchronous modems could run at speeds up to 9600 bit/s using phase-shift keying (PSK). Synchronous transmission used only slightly over 80% of the bandwidth of the now more-familiar asynchronous transmission, since start and stop bits were unnecessary. Those modems are obsolete, having been replaced by modems which convert asynchronous data to synchronous forms, but similar synchronous telecommunications protocols survive in numerous block-oriented technologies such as the widely used IEEE 802.2 (Ethernet) link-level protocol. USARTs are still sometimes integrated with MCUs. USARTs are still used in routers that connect to external CSU/DSU devices, and they often use either Cisco's proprietary HDLC implementation or the IETF standard point-to-point protocol (PPP) in HDLC-like framing as defined in RFC 1662.

Operation The operation of a USART is intimately related to the various protocols; refer to those pages for details. This section only provides a few general notes.

USARTs in synchronous mode transmits data in frames. In synchronous operation, characters must be provided on time until a frame is complete; if the controlling processor does not do so, this is an "underrun error," and transmission of the frame is aborted. USARTs operating as synchronous devices used either character-oriented or bit-oriented mode. In character (STR and BSC) modes, the device relied on particular characters to define frame boundaries; in bit (HDLC and SDLC) modes earlier devices relied on physical-layer signals, while later devices took over the physical-layer recognition of bit patterns. A synchronous line is never silent; when the modem is transmitting, data is flowing. When the physical layer indicates that the modem is active, a USART will send a steady stream of padding, either characters or bits as appropriate to the device and protocol.

Devices

References

Illustrations

Worked examples

Example 1 — a first encounter with Universal synchronous and asynchronous receiver-transmitter

Start with the simplest possible case. Write down what Universal synchronous and asynchronous receiver-transmitter claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Universal synchronous and asynchronous receiver-transmitter before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Universal synchronous and asynchronous receiver-transmitter ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Universal synchronous and asynchronous receiver-transmitter

In research: Universal synchronous and asynchronous receiver-transmitter appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Universal synchronous and asynchronous receiver-transmitter in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Universal synchronous and asynchronous receiver-transmitter is common in secondary-school and first-year university syllabi. It links to neighbouring topics Data transmission, so understanding it makes those chapters shorter.
In everyday life: Look for Universal synchronous and asynchronous receiver-transmitter outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Universal synchronous and asynchronous receiver-transmitter in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Universal synchronous and asynchronous receiver-transmitter means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Universal synchronous and asynchronous receiver-transmitter out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Universal synchronous and asynchronous receiver-transmitter in simple terms?

Why does Universal synchronous and asynchronous receiver-transmitter matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Universal synchronous and asynchronous receiver-transmitter?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Universal synchronous and asynchronous receiver-transmitter.