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Digital Communication
10 questions By Tony R. Kuphaldt
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Question 4 of 10
Personal computers and peripheral devices provide a rich source of examples for both serial and parallel data transmission. Identify some common examples of both serial and parallel data transmission networks (and standards) at work in a common personal computer. Examples may include communication between computers, between computers and peripheral devices (printers, scanners, cameras, special cards), or between fundamental components of the computer (CPU, disk drive, monitor, etc.).
Reveal answerExamples of serial data communication include the 9-pin and/or 25 pin “serial” connectors for RS-232C communication, Ethernet communication, USB ports, and most “mice.” Examples of parallel data communication include 25-pin “parallel” connectors to printer and scanner devices, and cables between motherboard and disk drives (legacy IDE technology).
Notes:As computer-savvy as most young students are, questions such as these tend to evoke ready responses and strong interest. You may find that little effort is required on your part to introduce these technologies to your students, as they may be more familiar with certain areas and features of it than you!
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Question 5 of 10
A ubiquitous example of serial data communication is the cable linking a keyboard to a personal computer: for every key switch pressed, an ASCII character is transmitted to the computer. An interesting characteristic of this particular communication protocol is the random rate at which the ASCII characters are sent. Because the characters are generated at the rate the computer user happens to type, the rate is completely unpredictable. Consequently, this form of serial data communication is known as asynchronous.
Compare and contrast this against synchronous serial data communication, giving an example of a synchronous data communications standard.
Reveal answerOne widespread synchronous data communications standard is SONET, used in long-distance data communication applications. I’ll let you do the research to compare and contrast synchronous against asynchronous.
Challenge question: the data sent between computers along serial-format networks such as RS-232C and Ethernet is “clocked” by precise oscillators at both the transmitting and receiving ends, yet is not considered “synchronous,” even if each byte of data is sent at regular (non-random) intervals. Explain why.
Notes:At first, it seems as though any communication between digital devices occurring at a pre-determined frequency (bps) and rate (characters per second) would be synchronous, because everything is happening on fixed intervals. However, the precision inherent to a true synchronous communications network is more rigorous than this. Let your students elaborate on what they have found through their research.
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Question 6 of 10
An important integrated circuit (IC) used in digital data communication is a UART. Describe what this acronym stands for, and explain the purpose of this circuit.
Reveal answer“UART” stands for Universal Asynchronous Receiver Transmitter, and its job is to act as an interface between two parallel-data devices, managing communications in serial format along a communication line of some sort.
Follow-up question: give an example of a UART IC available for purchase today.
Notes:When students research what a UART is, they will invariably stumble upon terms such as parity, start bit, and stop bit. If they are not yet familiar with the details of asynchronous data communications, this could lead to some enlightening discoveries. Be sure to discuss these terms and details with your students if they bring them up in class, because it means they will be very receptive to your instruction (having been “primed” for learning by wanting to know).
