1 DWT跟踪组件
2 Cortex-M中的DWT
3 使用方法
3.1 DEMCR
3.2 关于DWT_CYCCNT
3.3 关于CYCCNTENA
4 综上所述
先使能DWT外设，这个由另外内核调试寄存器DEMCR的位24控制，写1使能 使能CYCCNT寄存器之前，先清0。 使能CYCCNT寄存器，这个由DWT的CYCCNTENA 控制，也就是DWT控制寄存器的位0控制，写1使能
//0xE000EDFC DEMCR RW Debug Exception and Monitor Control Register.//使能DWT模块的功能位//0xE0001000 DWT_CTRL RW The Debug Watchpoint and Trace (DWT) unit//使能CYCCNT计数器开始计数//0xE0001004 DWT_CYCCNT RW Cycle Count register,//CYCCNT计数器的内部值(32位无符号)
vvolatile unsigned int *DWT_CYCCNT ;volatile unsigned int *DWT_CONTROL ;volatile unsigned int *SCB_DEMCR ;void reset_timer(){DWT_CYCCNT = (int *)0xE0001004; //address of the registerDWT_CONTROL = (int *)0xE0001000; //address of the registerSCB_DEMCR = (int *)0xE000EDFC; //address of the register*SCB_DEMCR = *SCB_DEMCR | 0x01000000;*DWT_CYCCNT = 0; // reset the counter*DWT_CONTROL = 0;}void start_timer(){*DWT_CONTROL = *DWT_CONTROL | 1 ; // enable the counter}void stop_timer(){*DWT_CONTROL = *DWT_CONTROL | 0 ; // disable the counter}unsigned int getCycles(){return *DWT_CYCCNT;}main(){....reset_timer(); //reset timerstart_timer(); //start timer//Code to profile...myFunction();...stop_timer(); //stop timernumCycles = getCycles(); //read number of cycles...}
/************ How to use:* uint32_t it1, it2; // start and stop flagstart_timer(); // start the timer.it1 = get_timer(); // store current cycle-count in a local// do somethingit2 = get_timer() - it1; // Derive the cycle-count differencestop_timer(); // If timer is not needed any more, stopprint_int(it2); // Display the difference****/
/* 初始化时间戳 */void CPU_TS_TmrInit(void){/* 使能DWT外设 */DEM_CR |= (uint32_t)DEM_CR_TRCENA;/* DWT CYCCNT寄存器计数清0 */DWT_CYCCNT = (uint32_t)0u;/* 使能Cortex-M3 DWT CYCCNT寄存器 */DWT_CR |= (uint32_t)DWT_CR_CYCCNTENA;}uint32_t OS_TS_GET(void){return ((uint32_t)DWT_CYCCNT);}
