physics

Synchronous serial communication

Synchronous serial communication is a physics 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 Synchronous serial communication rather than just read about it. In short: Synchronous serial communication describes a serial communication protocol, "In synchronous transmission, groups of bits are combined into frames, and frames are sent continuously with or without data to be transmitted." Synchronous communication requires that the clocks in the transmitting and receiving devices are synchronized – running at the same rate – so the receiver can sample the signal at the same time inte…

Key takeaways

Synchronous serial communication belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Synchronous serial communication to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Synchronous serial communication from memory before moving on to harder problems.

Reference excerpt

Synchronous serial communication describes a serial communication protocol, "In synchronous transmission, groups of bits are combined into frames, and frames are sent continuously with or without data to be transmitted." Synchronous communication requires that the clocks in the transmitting and receiving devices are synchronized – running at the same rate – so the receiver can sample the signal at the same time intervals used by the transmitter. No start or stop bits are required. For this reason, "synchronous communication permits more information to be passed over a circuit per unit time" than asynchronous serial communication. Over time the transmitting and receiving clocks will tend to drift apart, requiring resynchronization. Synchronous RS-232 used additional pins on the DB-25 cable: the DCE (generally the modem or other peripheral) provided two clock signals to the DTE (generally the host computer or terminal), transmitter clock (pin 15, TCK) and receiver clock (pin 17, RCK). Some systems supported an alternative mode of operation in which the transmitter clock signal was provided by the DTE instead, called transmitter timing (pin 24, TT). Note the smaller DE-9 connector commonly adopted in later systems does not have these additional signal lines, and hence cannot be used with synchronous RS-232.

Byte-oriented protocols Early synchronous protocols were byte-oriented protocols, where synchronization was maintained by transmitting a sequence of synchronous idle characters when the line was not actively transmitting data or transparently within a long transmission block. The bit pattern of these characters (0010110 in ASCII) was designed so that a receiver could determine where the breaks between bytes occurred within a series of them. The IBM Binary Synchronous protocol (Bisync) is still in use. Other examples of byte-oriented protocols are IBM's Synchronous transmit-receive (STR), and Digital Data Communications Message Protocol (DDCMP) from Digital Equipment Corporation. Other computer manufacturers often offered similar protocols, differing mainly in small details.

Bit-oriented protocols Bit-oriented protocols are synchronous protocols that view the transmitted data as a stream of bits with no semantics, or meaning. Control codes are defined in terms of bit sequences instead of characters. Synchronization is maintained on an idle line by transmitting a predefined sequence of bits. Synchronous Data Link Control (SDLC) specifies that a station continue transmitting a sequence of '1' bits on an idle line. Data to be transmitted on an idle line is prefixed with a special bit sequence '01111110'b, called a flag. SDLC was the first bit-oriented protocol developed, and it was later adopted by the International Organization for Standardization (ISO) as High-Level Data Link Control (HDLC). Other examples of bit-oriented protocols are Logical Link Control (LLC)—IEEE 802.2, and ANSI Advanced Data Communication Control Procedures (ADCCP).

References

See also Asynchronous serial communication Comparison of synchronous and asynchronous signalling Iteration Serial communication

Worked examples

Example 1 — a first encounter with Synchronous serial communication

Start with the simplest possible case. Write down what Synchronous serial communication claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, 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 Synchronous serial communication 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 Synchronous serial communication 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 Synchronous serial communication

In research: Synchronous serial communication appears in physics 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 Synchronous serial communication 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: Synchronous serial communication is common in secondary-school and first-year university syllabi. It links to neighbouring topics Data transmission, Physical layer protocols, Synchronization, so understanding it makes those chapters shorter.
In everyday life: Look for Synchronous serial communication 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 Synchronous serial communication in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Synchronous serial communication 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 Synchronous serial communication out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Synchronous serial communication in simple terms?

Why does Synchronous serial communication matter?

Because it connects several physics 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 Synchronous serial communication?

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 Synchronous serial communication.