CSE 237A Winter 2018 Homework 1

Transcription

1 CSE 237A Winter 2018 Homework 1 Problem 1 [10 pts] a) As discussed in the lecture, ARM based systems are widely used in the embedded computing. Choose one embedded application and compare features (e.g., speed, power, etc) and architecture elements (e.g., SIMD, RISC, etc) of the ARM processor with one of the DSPs discussed in class when it comes to that particular application. b) We also talked about Digital Signal Processor (DSP). Many DSP uses fixed-point design instead of floating-point. Give a practical application in which fixed point computation would be the right choice. List 3 major advantages and 3 drawbacks of the fixed-point design over the floating-point.

2 Problem 2 [10 pts] a) Modern embedded systems use different types of memories. Compare and contrast the following memories: i) SRAM ii) DRAM iii) Scratch pad memory iv) PCRAM Discuss i) how do they differ, ii) what are their common uses in a system design, and iii) list a few examples of embedded applications that would be benefit from each, and why. b) We also talked about various emerging non-volatile memory (NVM) technologies. The followings are some of the discussed NVMs: Memory STT-RAM (MRAM) PCRAM ReRAM Replacement candidate for current architecture SRAM cache replacement DRAM main memory and storage NAND flash, embedded NOR flash For each of the three memories, describe its key characteristics, and discuss/contrast why it is a suitable candidate for replacing conventional memory.

3 Problem 3 [10 pts] Assume an embedded system which consists of a sensor, an 8-bit A/D converter, and a single-core processor. The processor sequentially runs two tasks, an interrupt handler and an application. - The sensor outputs an analog voltage signal at a frequency of 50 khz - The A/D converter reads the sensor outputs and provides readings to the interrupt handler for the application. Then, the application can process each sample. - The maximum voltage that the A/D converter can read without quantization error is 5.1V, and the minimum is 0V - The interrupt handler processes each sample with 100 instructions - The processor can execute 1 instruction per cycle - The processor runs at 40 MHz Answer following questions. Show all work to get the full credit. a) What is the minimum sampling frequency of the A/D converter to avoid aliasing? b) What is the maximum quantization error of the A/D converter? What is the 8-bit representation of the voltage of 1.4 V? Assume that the A/D converter outputs for 0V. c) To read and process every sample without aliasing, what is the maximum number of instructions that can be executed by the application?

4 d) Let assume that the application executes 150 instructions. While running the interrupt handler and application, the processor is in active state. Once the application processes one sample, the processor can go to a sleep state until the next sample arrives from the A/D converter. i) Calculate average power consumption of the whole system. Use the table shown below and the sampling frequency obtained in part a) ii) Briefly discuss how the average power consumption changes if the A/D converter has higher sampling frequencies Sensor A/D converter Processor 5mW 50mW Active: 3 W / Sleep: 1 W

5 Problem 4 [10 pts] Consider that a single processor runs 3 periodic tasks which are defined in the table below. Worst case execution time (WCET) Period A 1 4 B 1 10 C 2 x a) Find the minimum period of task C, x, which fulfills the rate-monotonic inequality, where x is an integer. Show all work to get the full credit. Hint: 2 1/ ; 2 1/ ; 2 1/ x = b) Using x found in part a, fill tasks scheduled by RM in the table below. Assume the following: - All tasks arrive at the time t = 0. - If multiple tasks have the same priority, use alphabetic order to break the tie e.g., if task A and task B have the same priority, run task A first Time Time

6 c) What is the minimum period of the task C which is actually schedulable using RM? Is it the same as x found in part a? If not, fill the table below with the minimum period. Assume the following: - All tasks arrive at the time t = 0. - If multiple tasks have the same priority, use alphabetic order to break the tie e.g., if task A and task B have the same priority, run task A first The minimum period = Time Time Why? Show all work to get the full credit.

7 Problem 5 [10 pts] a) Given the three tasks, illustrate the Lamport s logical times on each dot b) For the same tasks, illustrate the timestamps using vector time on each dot