; SysTickTestMain.s
; Runs on LM4F120/TM4C123
; Test the SysTick functions by activating the PLL, initializing the
; SysTick timer, and flashing an LED at a constant rate.
; Daniel Valvano
; September 12, 2013

;  This example accompanies the book
;  "Embedded Systems: Introduction to ARM Cortex M Microcontrollers",
;  ISBN: 978-1469998749, Jonathan Valvano, copyright (c) 2014
;  Program 4.6, Section 4.3
;  Program 4.7, Section 4.4
;
;Copyright 2014 by Jonathan W. Valvano, valvano@mail.utexas.edu
;   You may use, edit, run or distribute this file
;   as long as the above copyright notice remains
;THIS SOFTWARE IS PROVIDED "AS IS".  NO WARRANTIES, WHETHER EXPRESS, IMPLIED
;OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF
;MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE.
;VALVANO SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL,
;OR CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.
;For more information about my classes, my research, and my books, see
;http://users.ece.utexas.edu/~valvano/

GPIO_PORTF_DATA_R EQU 0x400253FC

        IMPORT   SYSTICK_INIT
        IMPORT   SYSTICK_WAIT
        IMPORT   PRECISE_DELAY
		IMPORT   SYSTICK_READ
        IMPORT     GPIOF_INIT

        AREA    |.text|, CODE, READONLY, ALIGN=2
        THUMB
        EXPORT  __main
__main
    BL SYSTICK_INIT                ; initialize SysTick timer
    ; initialize Port F
prevent
	BL SYSTICK_READ
	BL SYSTICK_READ
	B prevent

    BL GPIOF_INIT

    LDR R4, =GPIO_PORTF_DATA_R            ;
    LDR R5, [R4]                    ; R5 = [R4]
loop
    EOR R5, R5, #0x04               ; R5 = R5^0x04 (toggle PF2)
    STR R5, [R4]                    ; [R4] = R5
    MOV R0, #2000                      ; Ask for 100 ms
    BL  PRECISE_DELAY
    B   loop

;-------------------------------------------------------------------
    ALIGN                           ; make sure the end of this section is aligned
    END                             ; end of file