$($a$)$ Write an assembly language function DIGJ.TS which will convert a $2-$digit decimal

number into the corresponding $2$ individual decimal digits. The input decimal

mumber is in R$10$ and the tens digit output is in R$11$ and the ones digit output

in R$12.$ Assume that there is no division and remainder instruction. You can

invent your own instruction set $2s$ long as it is reasonebie. $[4]$

$($b$)$ A party room cen ecommodate at most $70$ persons. There is a computer$-$

controlled turnstile in the entrance and exit to count the number of persons

entering and leaxing the party room. The number of persons currently in the

room is displayed on two $7-$segment. LEDS in front of the room. The turnstiles

have control and status regislers T$1$CSR $($entrance$)$ and T$2$CSR $($exit$)$ with the

following formal:

Bit $0$ Ready bit, the turnstile is reudy

Bit $1$ Set this bit to allow turnstile to turn

Bit $2$ Set this bit to disallow tumnstile to turn

Bit $3$ This bit is $1$ when one person has passed tiee turnstile, ard the

turnstile is disellowed automatically.

This bit will reset to zero after reading.

There are $2$ buffer registers $($daia registers$)$ for the LEDs, LEDBR$1($for the tens

digit$)$ and LEDBR$2($for the ones digit$).$ If the number of persons in the room is

$0,$ then display empyy on LEDBR$1$ and displey $0$ on LEDBR$2.$ To display empty

on an LED, just write FFFFFFFF to the buffer register.

Write an assembly lawguago program using Programmed I$/$O to do the following:

Initialization: Allow Entrance turnstile and disallow Exit turnstile. Set

number of persons, n$,$ to $0.$ Display $0$ on the LEDs.

Repeat:

$2\mathrm{.}1$ If $n=0$ disallow Lxit turnstile, otherwise allow it$.$

$2\mathrm{.}2$ If $n-70$ disallow Entrance turnstile, otherwise allow it$.$

$2\mathrm{.}3$ if someone passes Entrance turnsile:

$2\mathrm{.}3\mathrm{.}1$ disallow entrance turnstile

$2\mathrm{.}3\mathrm{.}2$nlarrn$-1$

$2\mathrm{.}3\mathrm{.}3$ display $n$ on LED

$2\mathrm{.}3\mathrm{.}4$ if $n+70$ anlow entrance tumstile again

$2\mathrm{.}4$ if someone passes Ex$$ turnstile:

$2\mathrm{.}4\mathrm{.}1$ disallow exit turnstile

$2\mathrm{.}1\mathrm{.}2n+n-1$

$2\mathrm{.}1\mathrm{.}3$ display $n$ on LED

$2\mathrm{.}4\mathrm{.}4$ if $n0$ allow exit turnstile sgain.

P$.6$ of $7$

You can invent your own instruction sct as long as it is reasoneble. You can

also use the function in $5(a)$ in your program. $10]$

$($c$)($i$)$ Why do we prefer register operands to memory operands for arithmetic$/$logic

operations? $[2]$

$($ii$)$ What is the advantage of a regular instruction format, i$.$e$.$ the source and

destination operands are always in the same place in the instruction.

$($iii$)$ Explain the difference between axithmetic shift and logical shift.