Problem $1.$ The PIC$24$ and the XC$16$ compiler assume multibyte values are stored in little$-$endian

form. For each of the following decimal values show how it is stored in data memory by listing the

contents of each byte used.

$($a$)$ The unsigned integer $9057$ at address $0$x$810.$

$($b$)$ The long integer$-13467$ at address $0$x$812.$

$($c$)$ The integer $2748$ at address $0$x$816.$

$($d$)$ The char E at address $0$x$818.($ASCII encoding$).$

Problem $2.$ Assume each instruction below is located at $0$x$000$bea. Using the Programmers

Reference Manual for the PIC$24,$ hand$-$assemble each of the following individual instructions.

$($a$)$ add #$0$xdb$,$ w$0$

$($b$)$ bra $0$x$037$a

$($c$)$ mov w$2,[$w$14]$

Problem $3.$ Foreachinstruction below assume initially $($PC$)=0$x$2$AE$,($SR$)=0$x$0000,($w$0)=0$xFFFF$,$

$($w$1)=0$x$080$A$,($w$15)=0$x$080$a$,$ and the contents of the $8$ sequential bytes in data memory begin

ning at $0$x$0806$ are $0$x$01,0$x$23,0$x$45,0$x$67,0$x$89,0$xAB, $0$xCD$,$ and $0$xEF. Give the contents of any

registers which have changed after each of the following instructions executes:

$($a$)$ mov.b #$0$x$12,$w$0$

$($b$)$ sub w$1,$w$0,$w$1$

$($c$)$ mov $[$w$15++],[--$w$1]$

$($d$)$ nop

$($e$)$ bra N$,0$x$0002$b$4$

Problem $4.$ Two $32-$bit signed integers in twos complement are to be added using a PIC$24$F

microcontroller. These two numbers, in hex, are $0$x$8$A$691$F$60$ and $0$x$20$B$7$C$050.$

$($a$)$ These two numbers are located in the $8$ sequential data RAM locations $0$x$800$ to $0$x$807.$ The

rst number, $0$x$8$A$691$F$60,$ is at address $0$x$800,$ the second number, $0$x$20$B$7$C$050,$ is at address

$0$x$804.$ Show the contents of memory locations $0$x$800$ to $0$x$807.$

$($b$)$ These two numbers are moved into the working registers with the double word move instruc

tions, mov.d $0$x$800,$w$0$ and mov.d $0$x$804,$w$2.$ Show the contents of registers w$0$ to w$3$ as $16-$bit

hex numbers after these move instructions execute.

$($c$)$ Thesequence of two instructions,

add w$0,$w$2,$w$0$

addc w$1,$w$3,$w$1$

are used to do the $32-$bit addition. What is the result of this addition $($as hex values$)$ found in

the register pair w$0$ and w$1$ immediately after these two instructions execute?

$($d$)$ The $32-$bit addition in $($c$)$ will a ect bits in the Status Register $($SR$).$ Immediately after the

addc instruction completes what are the values for the N$,$ OV$,$ Z$,$ and C bits in this register?

EE$2361$

Fall $2024$

Problem $5.$ The subroutine delay

listing of this subroutine is

$000002$f$4$ :

$2$f$4$: $004080$

sub uses a simple loop to implement a delay. The assembly

mov.w

$2$f$6$: f$1$ ff $2$f

$000002$f$8$ :

$2$f$8$: $008040$

$2$fa: $000000$

$2$fc: fd ff $3$a

$2$fe: $000006$

mov.w

add.w

nop

bra

return

count, w$0$

#$0$xffff$,$ w$1$

w$1,$ w$0,$ w$0$

NZ$,0$x$2$f$8$

Assume an instruction frequency of $16$ MHz for an an instruction cycle time of $62\mathrm{.}5$ ns$.$

$($a$)$ How many bytes of program memory does this subroutine, delay

bytes of data memory are used?

sub, occupy? How many

$($b$)$ What value should be used for the variable count if the delay is to be as close as possible to$,$

but no greater than, $10$ ms$?$

$($c$)$ To make this delay exactly $10$ ms we may need to add nop instruction$($s$).$ Where in the code

and how many nop instructions, if any, should be added?

$($d$)$ On exiting this subroutine, what are the values of the ALU bits $($N$,$ OV$,$ Z$,$ and C$),$ in the

status register?

$($e$)$ Can this subroutine be used to implement a $20$ ms delay? Suggest a simple way to do this