【FreeRTOS】prvStartFirstTask

 1 __asm void prvStartFirstTask( void )
 2 {
 3 /* *INDENT-OFF* */
 4     PRESERVE8
 5 
 6     /* Use the NVIC offset register to locate the stack. */
 7     ldr r0, =0xE000ED08  // 将 0xE000ED08 加载到 R0
 8     ldr r0, [ r0 ]    // 将 0xE000ED08 地址中的值，也就是向量表的实际地址加载到 R0
 9     ldr r0, [ r0 ]    // 根据向量表实际存储地址，取出向量表中的第一项，向量表第一项存储主堆栈指针 MSP 的初始值
10     /* Set the msp back to the start of the stack. */
11     msr msp, r0       // 将 MSP 的初始值写入 MSP 中
12 
13     /* Clear the bit that indicates the FPU is in use in case the FPU was used
14      * before the scheduler was started - which would otherwise result in the
15      * unnecessary leaving of space in the SVC stack for lazy saving of FPU
16      * registers. */
17     mov r0, #0
18     msr control, r0
19     /* Globally enable interrupts. */
20     cpsie i
21     cpsie f
22     dsb
23     isb
24     /* Call SVC to start the first task. */
25     svc 0
26     nop
27     nop
28 /* *INDENT-ON* */
29 }