Consider the following statements. I. Daisy chaining is used to assign…
2020
Consider the following statements.
I. Daisy chaining is used to assign priorities in attending interrupts.
II. When a device raises a vectored interrupt, the CPU does polling to identify the source of interrupt.
III. In polling,the CPU periodically checks the status bits to know if any device needs its attention.
IV. During DMA, both the CPU and DMA controller can be bus masters at the same time.
Which of the above statements is/are TRUE ?
Answer: C. Ⅰ and Ⅲ only — Answer: Statements I and III are true. I. Daisy chaining is used to assign priorities in attending interrupts — true. Devices are connected in series and…
- A.
Ⅰ and Ⅱ only
- B.
Ⅰ and Ⅳ only
- C.
Ⅰ and Ⅲ only
- D.
Ⅲ only
Attempted by 87 students.
Show answer & explanation
Correct answer: C
Answer: Statements I and III are true.
I. Daisy chaining is used to assign priorities in attending interrupts — true. Devices are connected in series and priority is determined by position in the chain.
II. When a device raises a vectored interrupt, the CPU does polling to identify the source of interrupt — false. For vectored interrupts the device or interrupt controller provides the interrupt vector/address, so the CPU can jump directly to the appropriate service routine without polling to find the source.
III. In polling, the CPU periodically checks the status bits to know if any device needs its attention — true. Polling is an active check by the CPU of device status registers.
IV. During DMA, both the CPU and DMA controller can be bus masters at the same time — false. DMA requires the DMA controller to take control of the bus to transfer data; the CPU is not a simultaneous bus master (it is suspended or uses schemes like cycle stealing, but only one master drives the bus at a time).
Therefore, only statements I and III are true.