Question

The FIFO status word is used to indicate the error in

(a) keyboard mode

(b) strobed input mode

(c) keyboard and strobed input mode

(d) scanned sensor matrix mode

This question was posed to me in an internship interview.

My doubt is from the Keyboard/Display Controller 8279 topic in section Special Purpose Programmable Peripheral devices and their Interfacing of Microprocessor

Answer 1

The correct answer is (c) keyboard and strobed input mode

To explain: Overrun error occurs when an already full FIFO has attempted an entry. Underrun error occurs when an empty FIFO read is attempted.