The ENTER EXIT the priority of short duration in R0 CRITICAL code, that how to ensure the CRITICAL region between the code does not use R0, is there not a problem if you use the

CodePudding user response:

Assembly code you see there is a corresponding C function prototype,

 uint32_t ulSetInterruptMask (void); 
Void vClearInterruptMask (uint32_t ulMask); 

UlSetInterruptMask has a return value, the return value is passed through R0, call ulSetInterruptMask when need to save the return value, and then restored, R0 of critical region is a free use,

 
Uint32_t saved; 
Saved=ulSetInterruptMask ();//enter the critical section, the current interrupt state is saved to the saved 
//critical region code, you can use the R0, 
VClearInterruptMask (saved);//exit the critical section, restore the interrupted status save