Engineering Questions with Answers - Multiple Choice Questions
MCQs on Interfacing I/O Ports
The device that enables the microprocessor to read data from the external devices is
Explanation: Since joystick is an input device, it reads data from the external devices.
The example of output device is
a) CRT display
b) 7-segment display
d) All of the mentioned
Explanation: The output device transfers data from the microprocessor to the external devices.
The input and output operations are respectively similar to the operations,
a) read, read
b) write, write
c) read, write
d) write, read
Explanation: The input activity is similar to read operation and the output activity is similar to write operation.
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
Explanation: IOWR (active low) operation means writing data to an output device and not an input device.
The latch or IC 74LS373 acts as
a) good input port
b) bad input port
c) good output port
d) bad output port
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.
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
Explanation: More current should not be sourced or sinked from data lines while reading to avoid loading.
To avoid loading during read operation, the device used is
d) tristate buffer
Explanation: A tristate buffer is used as an input device to overcome loading.
The chip 74LS245 is
a) bidirectional buffer
b) 8-bit input port
c) one that has 8 buffers
d) all of the mentioned
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.
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
Explanation: If DIR is 1, then the direction is from A(inputs) to B(outputs).
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
Explanation: In memory-mapped scheme, the devices are viewed as memory locations and are addressed likewise.