NOTE $2$: In writing the project code, use only the following instructions and their variations for conditional branching $($such as BEQ, BNE, etc$),$ conditional execution $($such as ADDEQ, etc$),$ size designation $($such as LDRH$,$ etc$),$ and flagging $($such as SUBS etc$)$: ADD, AND, B$,$ BL$,$ BX$,$ CMP$,$ EOR, LDR$,$ LSL$,$ LSR$,$ MOV, ORR, PUSH, POP, ROR, RRX$,$ STR$,$ and SUB.

No other instructions are allowed. Use of not$-$allowed instructions results in $0$ point.

A$.$ Problem

For a DE$1-$SoC system, write an ARM assembly code which down counts from a decimal number to $0$ by $1$ while displaying the numbers on the HEX$3-$HEX$07-$segments $($and$,$ optionally, at the same time on the VGA screen to earn extra $20$ points. See Note $3$ below for details of this option$).$ The starting number is determined by the positions of SW$3-$SW$0,$ SW$3$ being the $1000\text{'}$s position, SW$2$ being $100$s position, SW$1$ for $10$s$,$ and SW$0$ for units. The following example clarifies a decimal number obtained from SW positions:

$\backslash$table$[[$Number$,$SW$3,$SW$2,$SW$1,$SW$0],[-----,---,---,---,---],[1000,1,0,0,0],[1101,1,1,0,1],[0100,0,1,0,0]]$

Once the SW$3-$SW$0$ position determines the starting number, they are used no more. The counting down process pauses when SW$8$ is pressed $($i$.$e$.,$ SW$8=1)$ and resumes when SW$8$ is released $($SW$8=0).$ When testing your project code, after compilation, configure SW$3-$SW$0$ first, before running the code.

Note $3$: On the screen with background colored by the pixel color determined by the last fourdigits of your Howard ID$,$ display the numbers horizontally at $(10,20)$ location of the monitor. This option, if successfully implemented, earns extra $20$ points.

I NEED THIS ASAP