The Keyboard/Display Controller 8279 MCQ’s

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This set of Microprocessor Multiple Choice Questions & Answers (MCQs) focuses on “The Keyboard/Display Controller 8279″.

1. The sensor RAM acts as 8-byte first-in-first-out RAM in
a) keyboard mode
b) strobed input mode
c) keyboard and strobed input mode
d) scanned sensor matrix mode

2. The registers that hold the address of the word currently being written by the CPU from the display RAM are
a) control and timing register
b) control and timing register and timing control
c) display RAM
d) display address registers

3. The registers that store the keyboard and display modes and operations programmed by CPU are
a) I/O control and data buffers
b) Control and timing registers
c) Return buffers
d) Display address registers

4. When a key is pressed, a debounce logic comes into operation in
a) scanned keyboard special error mode
b) scanned keyboard with N-key rollover
c) scanned keyboard mode with 2 key lockout
d) sensor matrix mode

5. When a key is pressed, the debounce circuit waits for 2 keyboard scans and then checks whether the key is still depressed in
a) scanned keyboard special error mode
b) scanned keyboard with N-key rollover
c) scanned keyboard mode with 2 key lockout
d) sensor matrix mode

6. 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

7. The mode that is programmed using “end interrupt/error mode set command” is
a) scanned keyboard special error mode
b) scanned keyboard with N-key rollover
c) scanned keyboard mode with 2 key lockout
d) sensor matrix mode

8. The data that is entered from the left side of the display unit is of
a) left entry mode
b) right entry mode
c) left and right entry modes
d) none

9. The flag that increments automatically after each read or write operation to the display RAM is
a) IF
b) RF
c) AI
d) WF

10. If any change in sensor value is detected at the end of a sensor matrix scan, then the IRQ line
a) goes low
b) goes high
c) remains unchanged
d) none

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