Assembly Language Binary Adder

;This code was written for my Microprocessors/ Computer Architecture class last week.
;It was my first working assembly language code and it took two 2-bit binary numbers
;and added them together, lighting up three LEDs to show the output sum (also in binary).

;File: main.asm

;Desc: Lab 2 - 2 bit adder

;Date: 1 - 16 - 13

;Device: PIC18F1220

                        list       p=18F1220

                        radix    hex

                        config  WDT=OFF,LVP=OFF

#include "P18F1220.INC"

NUM1  equ 0x80

                        org 0x000                       ;Initialize I/O pins

                        CLRF  PORTB

                        MOVLW 0x7F               ;Digital I/O

                        MOVWF ADCON1       ;Digital I/O

                        MOVLW 0x0F

                        MOVWF TRISB            ;RB<3:0> inputs and RB<7:4> outputs

                        MOVLW 0x00              ;W=0

                        MOVWF NUM1           ;NUM1=0

Loop:   MOVF  PORTB,W                    ;Read PORTB

                        ANDLW 0x03               ;Clear upper 6 bits

                        MOVWF NUM1           ;NUM1=000000AA

                        MOVF PORTB,W         ;Read PORTB again

                        ANDLW 0x0C               ;WREG=0000BB00

                        RRNCF WREG

                        RRNCF WREG              ;WREG=000000BB

                        ADDWF NUM1,W        ;WREG=A+B

                        RRNCF WREG

                        RRNCF WREG

                        RRNCF WREG              ;A+B is in the upper 3 bits of WREG

                        MOVWF PORTB

                        GOTO  Loop

                        end

;Just to show off the beauty of fine engineering, here are a couple pictures of our final circuit:

;Such circuit. Much lights. So wow.