Engineering Questions with Answers - Multiple Choice Questions

MCQs on Interfacing with 8255

1 - Question

The 8255 is a ______ chip.
a) Input/Output
b) Analog to Digital
c) Digital to analog
d) None of the mentioned

View Answer

Answer: a
Explanation: The 8255 is Input/Output (I/O) chip. It has three separate accessible ports. The 8255 chip is used to expand the I/O ports of microcontrollers.




2 - Question

Which pins of a microcontroller are directly connected with 8255?
a) RD
b) WR
c) D0-D7
d) All of the mentioned

View Answer

Answer: d
Explanation: RD, WR, D0-D7 all are directly connected to the 8051 for telling the chip about the control signals and also for transferring the data.




3 - Question

Find the control word for PA= out, PB= in, PCL=out, PCH=out (Mode0)?
a) 0x02H
b) 0x82H
c) 0x83H
d) 0x03H

View Answer

Answer: b
Explanation: The value that is being loaded in the control word is 10000010b for PB as an input port and all others as the output ports being operated in mode0. The hex equivalent of 10000010b → 0x82H.




4 - Question

Which pins are used to select the ports and the control register?
a) CS
b) A1
c) A0
d) All of the mentioned

View Answer

Answer: d
Explanation: CS pin is an active low input pin for 8255 and it is used for selecting a chip. A0 and A1 pins are used for select ports and the control register.




5 - Question

What is the value of the control register when RESET button is set to zero?
a) 0x00H
b) 0xFFH
c) 0x11H
d) value remains the same

View Answer

Answer: d
Explanation: RESET is active-high signal input into the 8255 used to clear the control register. When RESET is activated (i.e. set to high), all ports are initialized as input mode. Hence the value of the control register remains the same as it is even when the RESET button is set to zero.




6 - Question

Why MOVX instruction is being used to access the ports of the 8255?
a) because 8255 is connecting a microcontroller in memory mapped I/O configuration
b) because 8255 is used to access the external communication
c) because 8255 is used to access the data transfer
d) because 8255 is used to access the interfacing of LCD, motor etc

View Answer

Answer: a
Explanation: As 8255 is connecting a microcontroller in memory mapped I/O configuration. This means that memory space used to access 8255 (i.e. 8255 is treated as external memory). MOVX instruction is used to access external memory locations.




7 - Question

What is correct about the BSR mode from below?
a) In BSR mode, only the individual bits of PORT A can be programmed
b) In BSR mode, only the individual bits of PORT B can be programmed
c) In BSR mode, only the individual bits of PORT C can be programmed
d) none of the mentioned

View Answer

Answer: c
Explanation: BSR (Bit Set/Rest) mode is used to program individual bits of PORT C only.




8 - Question

How many pins of the 8255 can be used as the I/O ports?
a) 8
b) 16
c) 24
d) 32

View Answer

Answer: c
Explanation: They are 3 ports available in the 8255 so 24 pins are available for the I/O ports pins.




9 - Question

8255 is a ____ pin IC.
a) 16
b) 8
c) 40
d) 60

View Answer

Answer: c
Explanation: 8255 is a 40 pin IC.




10 - Question

8255 has handshaking capability?
a) yes
b) no
c) cant be said
d) depends on the conditions

View Answer

Answer: a
Explanation: 8255 is a device that with the help of its handshaking property gets interfaced with any microcontroller.




11 - Question

The 8255 can be programmed in any of the __________
a) 2 modes
b) 3 modes
c) 4 modes
d) 5 modes

View Answer

Answer: c
Explanation: 8255 can be programmed in any of the 4 modes.

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