Two Marks Questions with Answers

Two Marks Questions with Answers

 

Q.l What are the basic modes of operation of 8255 ?

Ans. : There are two basic modes of operation of 8255, They are :

1. I/O mode. 2. BSR mode.

 

Q.2 Write the features of mode 0 in 8255 ?

Ans. :

1. Two 8-bit ports (port A and port B) and two 4-bit ports (port C upper and lower) are available. The two 4-bit ports can be combined used as a third 8-bit port.

2. Any port can be used as an input or output port.

3. Output ports are latched. Input ports are not latched.

4. A maximum of four ports are available so that overall 16 I/O configurations are possible.

 

Q.3 What are the features used mode 1 in 8255 ?

Ans. : Two groups-group A and group B are available for strobed data transfer.

1. Each group contains one 8-bit data I/O port and one 4-bit control/data port

2. The 8-bit data port can be either used as input or output port. The inputs and outputs both are latched.

3. Out of 8-bit port C, PC₀ -PC₂ is used to generate control signals for port B and PC3 = PC₅ are used to generate control signals for port A. The lines PC₆, PC₇ may be used as independent data lines.

 

Q.4 What are the signals used in input control signal and output control signal ?

Ans. : Input control signal :

1. STB (Strobe input)

2. IBF (Input buffer full)

3. INTR(Interrupt request)

Output control signal :

1. OBF (Output buffer full)

2. ACK (Acknowledge input)

3. INTR(Interrupt request)

 

Q.5 What are the features used mode 2 in 8255 ?

Ans. : The single 8-bit port in-group A is available.

1. The 8-bit port is bi-directional and additionally a 5-bit control port is available.

2. Three I/O lines are available at port C, viz PC₂-PC₀.

3. Inputs and outputs are both latched.

4. The 5-bit control port C (PC₃ = PC₇) is used for generating/accepting handshake signals for the 8-bit data transfer on port A.

 

Q.6 List the operation modes of 8255.

Ans. : a) I/O Mode

i. Mode 0-Simple Input/Output.

ii. Mode 1-Strobed Input/Output (Handshake mode)

iii. Mode 2-Strobed bidirectional mode

b) Bit Set/Reset Mode.

 

Q.7 What is a control word ?

Ans. : It is a word stored in a register (control register) used to control the operation of a program digital device.

 

Q.8 What is the purpose of control word written to control register in 8255 ?

Ans. : The control words written to control register specify an I/O function for each I/O port The bit D₇ of the control word determines either the I/O function of the BSR function.

 

Q.9 What is the size of ports in 8255 ?

Ans. :

Port-A : 8-bits

Port-B : 8-bits

Port-CU : 4-bits

Port-CL : 4-bits

 

Q.10 What is the use of stepper motor ?

Ans. : A stepper motor is a device used to obtain an accurate position control of rotating shafts. A stepper motor employs rotation of its shaft in terms of steps, rather than continuous rotation as in case of A.C. or D.C. motor.

 

Q.11 Define PPI.

Ans. : PPI means programmable parallel interface.

 

Q.12 Write down the function of  in 8255.

Ans. :  is an active low output which indicates that the CPU has written data into port.

 

Q.13 Write the BSR control words to set PC0 and to reset PC4 in 8255.

Ans. : BSR control word to set PC₀

 

 

 Q.14 What is the bit set reset mode of 8255 PPI ?

Ans. : The eight possible combinations of the states of bits D₃ - D₁ (B₂ B₁ B₀) in the Bit. Set-Reset format (BSR) determine particular bit in PC₀ - PC₇ being set or reset as per the status of bit D₀.

 

Q.15 Write the format of control word for 8255 PPI.

(Refer section 8.5)

 

Q.16 What are the ports available in 8255 ? What is the advantage of the third port ?

Ans. : The ports available in 8255 are : Port A, Port B and Port C. The advantages of third port, Port C is that it can be programmed for bit set/reset operation.

 

Q.17 What is handshaking and what are handshake signals ?

Ans. : Handshaking is the process of using signals to establish conditional data transfer. Devices provide signals called handshake signals to inform each other if they have any data available to send or if they are ready to accept data.

 

Q.18 Specify the bit of a control word for the 8255, which differentiates between I/O mode and the BSR mode.

Ans. : Bit D₇ in the control word. D₇ = 0 indicates bit set/reset mode and D₇ = 1 indicates I/O mode.

 

Q.19 What is the importance of handshake signals ?

Ans. : Handshake signals are used between two communicating devices to inform each other if they have any data available to send or if they are ready to accept data. These are very useful when two devices operate with different speed.

 

Q.20 What is the function of 8255 ?

Ans. : The function of 8255 is to provide microprocessor three different ways of parallel data transfer :

• Simple input/output

• Input/output with handshake

• Bi-directional I/O data transfer.

 

Q.21 Draw the command word format of 8255 in I/O mode.

(Refer section 8.5)

 

 

University Questions with Answers (Long Answered Questions)

 

(Regulation 2008)

Dec.-10

Q.1 Explain how the 8255 A progr 8085 microprocessor for reading

(Refer section 8.7)

May -11

Q.2 With neat block diagram, explain the operating modes of 8255 PPI.

(Refer section 8.6)        

Q.3 Explain the operation of 8255 of 8255 PPI Port A programmed as input and output in mode 1  with necessary handshaking signals.

(Refer section 8.6)        

Q.4 Explain in detail about various operating modes of 8255 PPI.

(Refer section 8.4)         

Q.5 Explain in detail, the operating  modes of 8255 PPI with control registers.

(Refer section 8.6)

May-13

Q.6 Draw and explain the functional block diagram of 8255 PPI.

(Refer section 8.3)

Dec.-13

Q.7 Draw and explain the functional block diagram of 8255 PPI

(Refer section 8.3)

Q.8 Explain in detail about various operating modes of 8255 PPI.

(Refer section 8.4)

May-14

Q.9 Draw and explain the functional block diagram of 8255 PPI.

(Refer section 8.3)

 

(Regulation 2013)

Q.9 Explain the architecture, function and registers of the 8255 PPI.

(Refer section 8.3)

Q.10 Explain the functioning of 8255 programmable peripheral interface and its modes.

(Refer section 8.4)

Q.11 Draw the block diagram of 8255(PPI) and explain its various operating modes.

(Refer sections 8.3 and 8.4)

May-18

Q.12 Draw the functional diagram of 8255 and explain its control word, modes of operation.

 (Refer sections 8.3, 8.4 and 8.5)

 

 (Regulation 2017)

Dec.-19

Q.13 Describe the operating modes and control words of 8255.

(Refer sections 8.4 and 8.5)