Suppose you are using SysTick in a busy-waiting method to periodically read a sensor value every 0.25 ms (i.e., initially, you are not using interrupts, but rather you are using a while busy-wait loop). a) Suppose you measured the microcontroller current and found it to be 200mA. If the microcontroller core voltage is 3.3V, what would be the microcontroller power consumption during the busy-waiting for the PWM method? Answer format: floating-point with at least two decimal places: Watts. b) Suppose you were not happy with the power consumption of the busy-waiting method. Therefore, you decided to implement periodic interrupt with SysTick. You write a SysTick ISR handler consisting of 400 instructions long. Suppose the microcontroller CPI average is 1.5. How many clock cycles does it take to execute your ISR handler? Answer format: integer c) How long doe it take to execute your ISR in microseconds if SysTick and the microcontroller are running at 48 MHz? us c) What percent of the time would the microcontroller spend executing your ISR? d) Suppose with your periodic interrupts method, you can put the microcontroller in low- power mode when waiting for interrupts (i.e., when it is not executing the timer handler). Furthermore, suppose the low-power mode consumes only 20% of the full-power mode exhibited in part (a) (i.e., busy-waiting). Then, what would you expect for the new power consumption with the periodic interrupts method? Answer format: floating-point with at least two decimal places: Watts e) What would be the percent power reduction from the busy-waiting method to the periodic interrupts method? Answer format: floating-point with at least two decimal places:

Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
Question

3

Suppose you are using SysTick in a busy-waiting method to periodically read a sensor value
every 0.25 ms (i.e., initially, you are not using interrupts, but rather you are using a while
busy-wait loop).
a) Suppose you measured the microcontroller current and found it to be 200mA. If the
microcontroller core voltage is 3.3V, what would be the microcontroller power consumption
during the busy-waiting for the PWM method?
Answer format: floating-point with at least two decimal places:
Watts.
b) Suppose you were not happy with the power consumption of the busy-waiting method.
Therefore, you decided to implement periodic interrupt with SysTick. You write a SysTick ISR
handler consisting of 400 instructions long. Suppose the microcontroller CPI average
is
1.5.
How many clock cycles does it take to execute your ISR handler? Answer format: integer
c) How long doe it take to execute your ISR in microseconds if SysTick and the
microcontroller are running at 48 MHz?
us
c) What percent of the time would the microcontroller spend executing your ISR?
d) Suppose with your periodic interrupts method, you can put the microcontroller in low-
power mode when waiting for interrupts (i.e., when it is not executing the timer handler).
Furthermore, suppose the low-power mode consumes only 20% of the full-power mode
exhibited in part (a) (i.e., busy-waiting). Then, what would you expect for the new power
consumption with the periodic interrupts method?
Answer format: floating-point with at least two decimal places:
Watts
e) What would be the percent power reduction from the busy-waiting method to the periodic
interrupts method?
Answer format: floating-point with at least two decimal places:
%
Transcribed Image Text:Suppose you are using SysTick in a busy-waiting method to periodically read a sensor value every 0.25 ms (i.e., initially, you are not using interrupts, but rather you are using a while busy-wait loop). a) Suppose you measured the microcontroller current and found it to be 200mA. If the microcontroller core voltage is 3.3V, what would be the microcontroller power consumption during the busy-waiting for the PWM method? Answer format: floating-point with at least two decimal places: Watts. b) Suppose you were not happy with the power consumption of the busy-waiting method. Therefore, you decided to implement periodic interrupt with SysTick. You write a SysTick ISR handler consisting of 400 instructions long. Suppose the microcontroller CPI average is 1.5. How many clock cycles does it take to execute your ISR handler? Answer format: integer c) How long doe it take to execute your ISR in microseconds if SysTick and the microcontroller are running at 48 MHz? us c) What percent of the time would the microcontroller spend executing your ISR? d) Suppose with your periodic interrupts method, you can put the microcontroller in low- power mode when waiting for interrupts (i.e., when it is not executing the timer handler). Furthermore, suppose the low-power mode consumes only 20% of the full-power mode exhibited in part (a) (i.e., busy-waiting). Then, what would you expect for the new power consumption with the periodic interrupts method? Answer format: floating-point with at least two decimal places: Watts e) What would be the percent power reduction from the busy-waiting method to the periodic interrupts method? Answer format: floating-point with at least two decimal places: %
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