Microprocessors Solved MCQs

1.

for i/o of 8255,if -----, the word is taken as a bit set/rest word

A. D7=1
B. D7=0
C. D0=1
D. D0=0
Answer» B. D7=0
2.

on activation of ----, 8255 loads data from the input port lines into the input buffer of that port

A. STB#
B. IBF
C. OBF#
D. none of these
Answer» B. IBF
3.

8255 has three ----parrallel port

A. 8bit
B. 16bit
C. 32bit
D. 64bit
Answer» A. 8bit
4.

in ----, bidirectional data transfer is possible

A. mode 0
B. mode1
C. mode2
D. BSR
Answer» C. mode2
5.

walkie-talkie is an example of …..serial communication

A. Simplex
B. Half duplex
C. Full Duplex
D. none of these
Answer» B. Half duplex
6.

Transmission through telephone lines is an example of….serial commuincation

A. Simplex
B. Half duplex
C. Full Duplex
D. none of these
Answer» C. Full Duplex
7.

Asynchronous serial communication involves

A. start bit
B. stop bits
C. character data
D. all of these
Answer» D. all of these
8.

to configure 8255 with port A output,Port B input port C lower output and port C upper input

A. Mov al,0AFH
B. mov al,0AEH
C. mov Al,0CEH
D. Mov A,0AAH
Answer» B. mov al,0AEH
9.

A high on ---line indicates that the buffer register is empty

A. TXRDY
B. TXE
C. TXC#
D. both B and C
Answer» B. TXE
10.

Adc 0808 uses ----technique

A. Successive apraximation
B. single step
C. dual slope
D. flash converter
Answer» A. Successive apraximation
11.

the signals provided by ADC are

A. SOC
B. EOC
C. ALE
D. all of these
Answer» D. all of these
12.

Flash ADC consist of….converters

A. 2^n
B. 2^n -1
C. 2^n +1
D. none of these
Answer» B. 2^n -1
13.

8253/54 has ----independent timers/counters

A. 1
B. 2
C. 3
D. 4
Answer» C. 3
14.

8253/54 timers can be programmed in---modes

A. 1
B. 3
C. 6
D. 5
Answer» C. 6
15.

in mode 0 of 8253/54 ----disables counting

A. gate=1
B. gate=0
C. wr#=1
D. wr#=0
Answer» B. gate=0
16.

8253/54 has c----command that allows the user to check the count value programmed mode and current status of the counter

A. write back
B. write ahead
C. read ahead
D. read back
Answer» D. read back
17.

for mode 3 of 8253/54, if the count is odd the output will be high for---

A. 2/(n+1)
B. (n+1)/2
C. 2/(n-1)
D. (n-1)/2
Answer» B. (n+1)/2
18.

EOC means

A. End of Conversion
B. Enable output conversion
C. error of conversion
D. none of these
Answer» A. End of Conversion
19.

ADC 0808 is ----- pin IC

A. 40
B. 20
C. 24
D. 28
Answer» D. 28
20.

ADC 0808 operates on single ---- power supply

A. 5V
B. 10V
C. 15V
D. 20V
Answer» A. 5V
21.

8255 has -------- i/o pins

A. 28
B. 26
C. 24
D. 22
Answer» C. 24
22.

8255 has three ----parallel ports

A. 8 bit
B. 16 bit
C. 32 bit
D. 64 bit
Answer» A. 8 bit
23.

In 8255 ,BSR means -----

A. bit set/reset
B. byteset/reset
C. binary set/reset
D. none
Answer» A. bit set/reset
24.

BSR mode is used to set or reset the bitsin

A. portA
B. portB
C. portC
D. portD
Answer» C. portC
25.

8255 has ----i/o modes

A. 2
B. 3
C. 4
D. 8
Answer» B. 3
26.

A high on ----pin causes all 24 lines of three 8 bit ports to be in the input mode

A. WR\
B. RESET
C. GND
D. Vcc
Answer» B. RESET
27.

For i/o mode of 8255,if -----,the word is taken as a mode definition word

A. D7=1
B. D7=0
C. D0=1
D. D0=0
Answer» A. D7=1
28.

For i/o mode of 8255 ,if -----, the word is taken as a bit set/reset word

A. D7=1
B. D7=0
C. D0=1
D. D0=0
Answer» B. D7=0
29.

On activation of --------,8255 loads data from the input port lines into the input buffer of that port

A. STB\
B. IBF
C. OBF\
D. NONE
Answer» B. IBF
30.

IBF is an active-------- output signal for 8255

A. high
B. low
C. enable
D. disable
Answer» A. high
31.

8255 sets INTR when STB'=-----,IBF=---------,INTE=--------,for input conrol signals

A. 1,0,1
B. 1,1,0
C. 1,1,1
D. 0,1,1
Answer» C. 1,1,1
32.

Upon activation of------ signal,output device reads data from output port and acknowledges it

A. INTR
B. ACK\
C. OBF\
D. IBF
Answer» C. OBF\
33.

In ------ of 8255 ,bidirectionali/o data transfer is possible

A. mode0
B. mode1
C. mode2
D. BSR MODE
Answer» C. mode2
34.

Walkie-talkie is an example of serial communication

A. simplex
B. half-duplex
C. full-duplex
D. none
Answer» B. half-duplex
35.

Asynchronous serial communication involves transmission of

A. start bit
B. stop bit
C. character data
D. all
Answer» D. all
36.

Whichof the following is the fastest ADC

A. DUAL SLOPE
B. successive approximation
C. flash
D. single slope
Answer» C. flash
37.

To indicate end of conversion ADC 0808/0809 ACTIVATES -----SIGNAL

A. EOC
B. SOC
C. CLK
D. OUTPUT CONTROL
Answer» A. EOC
38.

Conversion time Tc of successive approximation ADC is given as

A. T(n-1)
B. T(n+1)
C. T(n)
D. T(n+2)
Answer» B. T(n+1)
39.

Conversion time of ADC 0808 IS

A. 100 ms
B. 100micro sec
C. 100 Ms
D. 100ns
Answer» B. 100micro sec
40.

ADC 0809 IS A ----- PIN IC

A. 40
B. 20
C. 24
D. 28
Answer» D. 28
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