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(COMP355)[2010](s)midterm~id-^_10211.pdf
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COMP 355 Embedded Systems Software
Spring Semester 2010
M:\courses\comp355\Others\ARM\SamekPart6Fig2.jpg
Midterm Examination
Date: 24 Mar. 2010 Time: 4:30 pm - 5:50 pm
Name:___SOLUTION________ Student ID: ________________Email:____________________
Instructions
1. Please write your name, student ID and email address on this page.
2. Please answer all the questions within the space provided on the examination paper. You may use the back of the pages for your rough work.
3. This paper consists of 8 questions and 6 pages.
4. Please read each question very carefully and answer the questions carefully and clearly to the point. Make sure your answers are neatly written, legible and readable.
5. Show all the steps used in deriving your answer, wherever appropriate.
Question
Points
Score
1
10
2
10
3
10
4
10
5
10
6
10
7
20
8
20
Total
100
1. (10 points) Recently Apple announced the iPad, which we can view as an embedded system. Among the characteristics of embedded systems that are listed on p. 22-24 of the Introduction chapter, which do you think apply to the iPad? Briefly justify your choices.
Power: The portable device will have to run on a battery source that should have significant lifetime per charge.
Cost: Since this is a specialized device, users would not be willing to pay a large price.
Memory size: finite size and fully embedded into the system. Secondary storage is not available.
Performance and Reliability will not pose a significant limitation on the system, although users still expect a certain level of performance and reliability from the device.
(2 pts each for the characteristics, 2 pts each for reasoning, 2 points for the last sentence)
2. (10 points) All ARM processors have only two interrupt pins (IRQ and FIQ (fast interrupt request)). How can we interface multiple I/O devices with the ARM processor?
Answer: Use a interrupt controller to interface the multiple I/O devices. An example:
3. (10 points) The following questions pertain to I/O transfers:
a) (2.5 pts) While the CPU is sleeping in power-saving mode, can DMA transfers continue? Briefly explain in one or two sentences.
Yes, DMA does not need the involvement of CPU during data transfers.
b) (2 pts) Is the time for one iteration of the do loop for programmed I/O on p. 12 constant? Briefly justify your answer in one or two sentences.
No. It is dependent on how many of the I/O devices have input/output that needs to be handled.
c) (2.5 pts) Will DMA based I/O also requires the use of interrupt handlers? Briefly explain your answer in one or two sentences.
Yes, there will be an interrupt at the end of DMA operation.
d) (3 pts) One of my colleagues claims that interrupt handling can be considered as a h