$4.$ The following code is executed in a PIC$24$H processor with Fosc$=25$MHz:

void $\_$ISRFAST $\_$T$2$Interrupt $($void$)\{$

update$\_$state$()$;

$\_$T$2$IF $=0$; $\}$

int main $($void$)\{$

T$2$CON$=0$x$0020$; $/$

PR$2=1562$;

TMR$2=0$;

$\_$T$2$IF $=0$;

$\_$T$2$IP $=1$;

$\_$T$2$IE $=1$;

T$2$CONbits.TON $=1$;

while $(1)\{$

$//....$ other code in the program

$\}$

$\}$

King Saud University Semester I, $1446$ H

College of Computer and Information Sciences CEN$318$: Design of Embedded Systems

Computer Engineering Department Homework $3$

Compute the percentage of CPU time taken by the ISR. Assume the function call update$\_$state$()$

consumes $50$ instruction cycles and all other statements consume one instruction cycle.