PENDSV异常处理程序中,如下红色标记,为何要使用2次同样的语句呢???? 我屏蔽了一句以后,发现程序无法正常运行,而且串口提示 。 \ | / - RT - Thread Operating System / | \ 0.4.0 build Feb 15 2012 2006 - 2009 Copyright by rt-thread team psr: 0x200000bc pc: 0x00010088 lr: 0x41f0e92d r12: 0x0064656c r03: 0x00000014 r02: 0x00000014 r01: 0x00010002 r00: 0x00010003 hard fault on thread: led rt_hw_pend_sv PROC ;pendSV异常处理程序 EXPORT rt_hw_pend_sv ; disable interrupt to protect context switch 关闭中断,保护线程切换 MRS r2, PRIMASK CPSID I ; get rt_thread_switch_interrupt_flag 获取线程中断切换标志 LDR r0, =rt_thread_switch_interrput_flag LDR r1, [r0] CBZ r1, pendsv_exit ; pendsv already handled CBZ 比较,结果为0 就转移到PENDSV_EXIT ; clear rt_thread_switch_interrput_flag to 0 清零线程中断切换标志 MOV r1, #0x00 STR r1, [r0]; 先清0,提示工作完成,之后再开始处理 LDR r0, =rt_interrupt_from_thread ; LDR r1, [r0] CBZ r1, swtich_to_thread ; skip register save at the first time 如果rt_interrupt_from_thread为0,则为第一次上下文切换 MRS r1, psp ; get from thread stack pointer STMFD r1!, {r4 - r11} ; push r4 - r11 register LDR r0, [r0] STR r1, [r0] ; update from thread stack pointer swtich_to_thread LDR r1, =rt_interrupt_to_thread ;rt_interrupt_to_thread地址传给R1 LDR r1, [r1] ;将rt_interrupt_to_thread地址上的值传给R1 LDR r1, [r1] ; Load thread stack pointer //为什么要用两次LDR命令呢??;将rt_interrupt_to_thread地址上的值作为地址时上的值 写入到R1。 /*上面这句如果用c语言表示就是 int32 *rt_interrupt_to_thread; r1=&rt_interrupt_to_thread; r1=*(r1); r1=*(r1); */ 不知道这样理解是否正确呢? LDMFD r1!, {r4 - r11} ; pop r4 - r11 register MSR psp, r1 ; update stack pointer pendsv_exit ; restore interrupt MSR PRIMASK, r2 ORR lr, lr, #0x04 BX lr ENDP
[ 本帖最后由 flyword 于 2012-2-15 20:56 编辑 ]