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		TTL Lab 5 Exercise 3 Calculate Average
;***************************************************************
;This file provides some pre-defined assembly instructions that
;students can add to in order to perform an averaging tasks.
; //By A. Mason, Aug 2017//
;***************************************************************
;Assembler directives
            THUMB
;***************************************************************
;EQUates
;Vectors
VECTOR_TABLE_SIZE EQU 0x000000C0  ;KL25Z
VECTOR_SIZE       EQU 4           ;Bytes per vector
;Memory
SSTACK_SIZE EQU  0x00000100
;NVIC
ICER		EQU	 0xE000E180
;**********************************************************************
;Vector Table Mapped to Address 0 at Reset
;Linker requires __Vectors to be exported
            AREA    RESET, DATA, READONLY
            EXPORT  __Vectors
__Vectors
            DCD  SP_INIT        ;stack pointer value when stack is empty
            DCD  Reset_Handler  ;reset vector
			SPACE  (VECTOR_TABLE_SIZE - (2 * VECTOR_SIZE))
            ALIGN
;**********************************************************************
            AREA    RAM,DATA,READWRITE
;Allocate system stack
SSTACK      SPACE   SSTACK_SIZE
SP_INIT
;Variables go here
RAM_Data    SPACE   64    ;reserve space for 64 variables @ label Ram_Data

;**********************************************************************
;Program
;Linker requires Reset_Handler
            AREA    StudentCode,CODE,READONLY
            ENTRY
            EXPORT  Reset_Handler

Reset_Handler
			CPSID   I       ;Mask interrupts
; DISABLE INTERRUPTS
			LDR 	R0, =ICER 	;R0 = &ICER
			MOVS 	R1,	#0 		; R1 = 0
			MVNS 	R1, R1 		; R1 = 0xFFFFFFFF
			STR 	R1, [R0, #0]; ICER = 0xFFFFFFFF
; INIT STACK POINTER
			LDR R0, =SP_INIT 	; load base address
			MOV SP, R0		; set SP to base address

;**********************************************************************
;*Top of User Code*****************************************************
;**********************************************************************
Main
; Load constants
			LDR		R6, =ROM_Con
			LDR		R7, =RAM_Data

; add student code below
			LDR		R3, =0x00000000 ; I forgot
			LDR		R4, =0x00000000 ; Running total
			LDR		R5, =0x00000000 ; Counter variable

looptime
			LDRB	R2,[R6]
			ADDS	R6, R6, #1 ; Increments address
			ADDS	R5, R5, #1 ; Increments counter
			ADDS	R4, R4, R2	; Add the currently loaded value to the sum register
			CMP 	R5, #8
			BNE 	looptime
			LSRS	R4, R4, #3
			STR		R4, [R7]
; Leave the next two lines at the end of all Main code
            B     	.
            ALIGN

;**********************************************************************
;ROM Constants go below
;**********************************************************************
ROM_Con ;address label for constants stored in ROM
			DCB		1, 6, 2, 9	;will store each decimal value as a hex byte
			DCB		7, 0, 3, 4
			ALIGN 	; NEEDED AFTER CONSTANTS ARE DECLARED
			END