Two Marks Questions with Answers

Two Marks Questions with Answers

 

Q.1 What is meant by polling ?

Ans. : Polling or device polling is a process which identifies the device that has interrupted the microprocessor.

 

Q. 2 What is interrupt ?

Ans. : Interrupt is an external signal that causes a microprocessor to jump to a specific subroutine.

 

Q.3 Differentiate between software and hardware interrupts.

Ans. : The type of interrupts where microprocessor pins are used to receive interrupt requests, are called hardware interrupts. In software interrupts, the cause of the interrupt is an execution of the instruction. These are special instructions supported by the microprocessor. After execution of these instructions microprocessor completes the execution of the instruction it is currently executing and transfers the program control to the subroutine program.

 

Q.4 Name the vectored and nonvectored interrupt of 8085 system.

AU : May-05, Dec.-17

Ans. : Vectored interrupt of 8085 are : RSTO - RST7, TRAP, RS7.5, R6.5 and RST 5.5. The only nonvectored interrupt of 8085 system is INTR.

 

Q.5 What are all the hardware interrupts ?

(Refer section 4.2.2.1)

 

Q.6 What is meant by level-triggered interrupt ? Which of the interrupts in 8085 are level triggered ?

Ans. : A level triggered interrupt is an interrupt signalled by maintaining the interrupt line at a high or low level. A device wishing to signal a level triggered interrupt drives the interrupt request line to its active level (high or low), and then holds it at that level until it is recognized by microprocessor. In 8085 microprocessor, RST 5.5, RST 6.5, INTR and TRAP are level triggered interrupts. Note that trap is both level as well as edge triggered interrupt.

 

Q.7 What is meant by edge-triggered interrupt ? Which of the interrupts in 8085 are edge triggered ?

Ans. : An edge-triggered interrupt is an interrupt signalled by a level transition on the interrupt line, either a falling edge (high to low) or a rising edge (low to high). A device, wishing to signal an interrupt, drives a pulse onto the line and then releases the line to its inactive state. In 8085 microprocessor, RST 7.5 and trap are edge-triggerred interrupts.

 

Q.8 What is TRAP interrupt and its significance ?

(Refer section 4.2)

 

Q.9 What do you mean by maskable and non maskable interrupts ?

Ans. :          • In the processor those interrupts which can be masked under software control are called maskable interrupts.

• The interrupts which cannot be masked under software control are called non-maskable interrupts.

 

Q.10 List two major differences between INTR and the other hardware interrupts.

AU : Dec.-19

Ans. : INTR is not a vector interrupt. On the other hand, other hardware interrupts are vector interrupts. INTR cannot be individually masked. On the other hand, other maskable hardware interrupts such as RST 5.5, RST 6.5 and RST 7.5 can be individually masked.

 

Q.11 Differentiate programmed I/O and interrupt driven I/O.    

Ans :