start.s

RT-Thread是发展中的下一代微内核嵌入式实时操作系统

/*
 * File      : start.S
 * This file is part of RT-Thread RTOS
 * COPYRIGHT (C) 2006, RT-Thread Development Team
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://openlab.rt-thread.com/license/LICENSE
 *
 * Change Logs:
 * Date           Author       Notes
 * 2006-09-23     Vai      first version (For ARM7TDMI core)
 */

 .globl _entry;
 _entry:
    mov r0, #0x12       @ Switch to IRQ MODE
    msr cpsr, r0        
    ldr sp, =__sp_irq   @ Set stack pointer for IRQ mode

    mov r0, #0x1f       @ Switch to SVC32
    msr cpsr, r0
    ldr sp, =__sp_svc   @ Set stack pointer for SVC mode

    /* Then Clear BSS section */
    mov r0, #0
    ldr r1, =__bss_start
    ldr r2, =_end
1:  cmp r1, r2
    strcc r0, [r1], #4
    bcc 1b

    /* Jump to main function */
    b   main


/* Special SWI */
.globl  swiDelay
swiDelay:
    swi 0x030000
    bx  lr

.globl  swiIntrWait
swiIntrWait:
    swi 0x040000
    bx  lr

.globl  swiWaitForVBlank
swiWaitForVBlank:
    swi 0x050000
    bx  lr