Microprocessors Questions and Answers – Interfacing I/O Ports

This set of Microprocessor Multiple Choice Questions & Answers (MCQs) focuses on “Interfacing I/O Ports”.

1. The device that enables the microprocessor to read data from the external devices is
a) printer
b) joystick
c) display
d) reader
View Answer

Answer: b
Explanation: Since joystick is an input device, it reads data from the external devices.

2. The example of output device is
a) CRT display
b) 7-segment display
c) Printer
d) All of the mentioned
View Answer

Answer: d
Explanation: The output device transfers data from the microprocessor to the external devices.

3. The input and output operations are respectively similar to the operations,
a) read, read
b) write, write
c) read, write
d) write, read
View Answer

Answer: c
Explanation: The input activity is similar to read operation and the output activity is similar to write operation.
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4. The operation, IOWR (active low) performs
a) write operation on input data
b) write operation on output data
c) read operation on input data
d) read operation on output data
View Answer

Answer: b
Explanation: IOWR (active low) operation means writing data to an output device and not an input device.

5. The latch or IC 74LS373 acts as
a) good input port
b) bad input port
c) good output port
d) bad output port
View Answer

Answer: c
Explanation: If the output port is to source large currents, the port lines must be buffered. So, the latch is used as it acts as a good output port.
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6. While performing read operation, one must take care that much current should not be
a) sourced from data lines
b) sinked from data lines
c) sourced or sinked from data lines
d) sinked from address lines
View Answer

Answer: c
Explanation: More current should not be sourced or sinked from data lines while reading to avoid loading.

7. To avoid loading during read operation, the device used is
a) latch
b) flipflop
c) buffer
d) tristate buffer
View Answer

Answer: d
Explanation: A tristate buffer is used as an input device to overcome loading.
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8. The chip 74LS245 is
a) bidirectional buffer
b) 8-bit input port
c) one that has 8 buffers
d) all of the mentioned
View Answer

Answer: d
Explanation: The chip 74LS245 is a bidirectional buffer that contains 8 buffers and may be used as an 8-bit input port. But while using as an input device, only one direction is useful.

9. In 74LS245, if DIR is 1, then the direction is from
a) inputs to outputs
b) outputs to inputs
c) source to sink
d) sink to source
View Answer

Answer: a
Explanation: If DIR is 1, then the direction is from A(inputs) to B(outputs).
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10. In memory-mapped scheme, the devices are viewed as
a) distinct I/O devices
b) memory locations
c) only input devices
d) only output devices
View Answer

Answer: b
Explanation: In memory-mapped scheme, the devices are viewed as memory locations and are addressed likewise.

Sanfoundry Global Education & Learning Series – Microprocessors.

Here’s the list of Best Books in Microprocessors.

To practice all areas of Microprocessors, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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