Engineering Questions with Answers - Multiple Choice Questions

# MCQs on Programmable Interval Timer 8254

1 - Question

The number of counters that are present in the programmable timer device 8254 is
a) 1
b) 2
c) 3
d) 4

Explanation: There are three counters that can be used as either counters or delay generators.

2 - Question

The operation that can be performed on control word register is
b) write operation
d) none

Explanation: The control word register can only be written and cannot be read.

3 - Question

The mode that is used to interrupt the processor by setting a suitable terminal count is
a) mode 0
b) mode 1
c) mode 2
d) mode 3

Explanation: Mode 0 is also called as an interrupt on the terminal count.

4 - Question

In mode 2, if N is loaded as the count value, then after (N-1) cycles, the output becomes low for
a) 1 clockcycle
b) 2 clockcycles
c) 3 clockcycles
d) 4 clockcycles

Explanation: After (N-1) cycles, the output becomes low for only 1 clockcycle. If the count N is reloaded and again the output becomes high and remains so for (N-1) clock pulses.

5 - Question

The generation of a square wave is possible in the mode
a) mode 1
b) mode 2
c) mode 3
d) mode 4

Explanation: When the count N loaded is even, then for half of the count, the output remains high and for the remaining half it remains low. If the count loaded is odd, the first clock pulse decrements it by 1 resulting in an even count value.

6 - Question

In control word register, if SC1=0 and SC0=1, then the counter selected is
a) counter 0
b) counter 1
c) counter 2
d) none

Explanation: SC denotes select counter.

7 - Question

In control word format, if RL1=1, RL0=1 then the operation performed is

Explanation: To access 16 bit, first LSB is loaded first, and then MSB.

8 - Question

If BCD=0, then the operation is
a) decimal count
c) binary count
d) octal count

Explanation: If BCD=0 then hexadecimal count. If BCD=1, then the operation is BCD count.

9 - Question

The counter starts counting only if
a) GATE signal is low
b) GATE signal is high
c) CLK signal is low
d) CLK signal is high

Explanation: If the GATE signal is enabled, then the counter starts counting.

10 - Question

The control word register contents are used for
a) initializing the operating modes
b) selection of counters
c) choosing binary/BCD counters
d) all of the mentioned