Lab2_DeanNguyen

# -------------------------------------------------------------------------
# Name: Dean Nguyen
# Date: 9/19/2019
# File: HexIncDec.s
# Desc: Assembly language program that increments/decrements hex value.
# Sets: SW0 High = Increment, SW0 Low = Decrement, KEY1 (Active) High = Change, KEY1 Low = No Change
# -------------------------------------------------------------------------

.data
.text

# define a macro to move a 32 bit address to a register

.macro MOVIA reg, addr
  movhi \reg, %hi(\addr)
  ori \reg, \reg, %lo(\addr)
.endm

# define constants
.equ Switches, 0x11020    #find the base address of Switches in the system.h file
.equ Hex0, 0x11000        #find the base address of Hex0 in the system.h file
.equ Pushbuttons, 0x11010 #find the base address of Pushbuttons in the system.h file
.equ SW0_HI, 1            #set SW0_HI as 1
.equ KEY1_HI, 15          #set KEY1_HI as 15
.equ lowNum, 64           #set lowNum as 64
.equ highNum, 24          #set highNum as 24

# define main program
.global main

# notes:
# r9 = load 'SSDconstants'
# r10 = load 'Switches'
# r11 = load 'Pushbuttons'

main:
   movia r2, Switches     #load r2 with 'Switches' address
   movia r3, Hex0         #load r3 with 'Hex0' address
   movia r4, Pushbuttons  #load r4 with 'Pushbuttons' address
   movia r5, SSDconstants #load r5 with 'SSDconstants' array
   movia r6, SW0_HI       #load r6 with 'SW0_HI' constant
   movia r7, KEY1_HI      #load r7 with 'KEY1_HI' constant
   movia r8, lowNum       #load r8 with 'lowNum' constant
   movia r12, highNum     #load r12 with 'highNum' constant

loop:
   ldbio r9, 0(r5) #load 'SSDconstants' into r9
   stbio r9, 0(r3) #store r9 into 'Hex0'
   ldbio r10, 0(r2) #load 'Switches' into r10
   andi r10, r10, 1 #bitmask SW0 (0000000#)
   ldbio r11, 0(r4) #load 'Pushbuttons' into r11
   ori r11, r11, 13 #bitmask KEY1 (11#1)
   beq r11, r7, direction #branch to 'direction' if KEY1 is not pressed
   br loop #go back to beginning of 'loop'

direction:
   beq r10, r0, decrement #branch to 'decrement' if SW0 is low
   beq r10, r6, increment #branch to 'increment' if SW0 is high

decrement:
   beq r9, r8, errorCheck #branch to 'errorCheck' if SSD is on 0
   subi r5, r5, 4 #decrement array
   br loop #go back to beginning of 'loop'

increment:
   beq r9, r12, errorCheck #branch to 'errorCheck' if SSD is on 9
   addi r5, r5, 4 #increment array
   br loop #go back to beginning of 'loop'

errorCheck:
   br loop #go back to beginning of 'loop'

SSDconstants:
   .word 64, 121, 36, 48, 25, 18, 2, 120, 0, 24 #from zero to nine