Consider a system built on a $48MHz$ processor with a main loop and an interrupt which occurs at aSuppose the SysTick interrupt occurs when PC $=008000044,xPSR=000000020,SP=020000200,$

$LR=008001000,$ and $Ri=i(i=0,1,2,$dots,$12).$

$6\mathrm{.}1.$ Show the stack content and the value of PC and SP when immediately entering the SysTick

interrupt service routine.

$6\mathrm{.}2.$ When executing the instruction $"BxLR",$ how does the processor know whether it is exiting a

standard subroutine or an interrupt service routine? What operations are performed when exiting

a standard subroutine? What operations are performed when exiting an interrupt service

routine$($ISR$)?$

$10kHz$ frequency. Assume the ISR take $14\mathrm{.}9$us to execute and there is a total of $1$us of response and

return time overhead.

$1\mathrm{.}1.$ What percentage of the processor's time is spent in interrupt response and return overhead?

$1\mathrm{.}2.$ What percentage of the processor's time is left for the main loop to execute?

$1\mathrm{.}3.$ If the main loop requires $37ms$ of computation to execute one iteration, what is the minimum main loop

update rate $($in $Hz)?$