;/*****************************************************************************/
; OSasm.s: low-level OS commands, written in assembly                       */
; Runs on LM4F120/TM4C123/MSP432
; Lab 4 starter file
; March 25, 2016

;


        AREA |.text|, CODE, READONLY, ALIGN=2
        THUMB
        REQUIRE8
        PRESERVE8

        EXTERN  RunPt            ; currently running thread
        EXPORT  StartOS
        EXPORT  SysTick_Handler
        IMPORT  Scheduler


SysTick_Handler                ; 1) Saves R0-R3,R12,LR,PC,PSR
    CPSID   I                  ; 2) Prevent interrupt during switch
    ;YOU IMPLEMENT THIS (same as Lab 3)
    CPSIE   I                  ; 9) tasks run with interrupts enabled
    BX      LR                 ; 10) restore R0-R3,R12,LR,PC,PSR

StartOS
    ;YOU IMPLEMENT THIS (same as Lab 3)
    CPSIE   I                  ; Enable interrupts at processor level
    BX      LR                 ; start first thread

    ALIGN
    END