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obtaining cycle count on cortex m7

Pallavi boreddy

hi

I have executed a cmsis dsp absolute function on cortex m7 (arm_abs_q7) and obtained the states as 860 ( as it indicates approximated cycle count). when i re-run the same function, i get the varying states.why is it so. i am using simulator mode for debug, where memory is not accessed. to access the memory i have used the following kernel code to enable DWT register
// variable definitions
uint32_t clock_cycles_counter;
volatile unsigned int *DWT_CYCCNT = (uint32_t *)0xE0001004; //address of the register
volatile unsigned int *DWT_CONTROL = (uint32_t *)0xE0001000; //address of the register
volatile unsigned int *SCB_DEMCR = (uint32_t *)0xE000EDFC; //address of the register

[...]

// configure and start the clock cycles counter
clock_cycles_counter = 0;
*SCB_DEMCR = *SCB_DEMCR | 0x01000000;
*DWT_CYCCNT = 0;
*DWT_CONTROL |=  1;

// do something
algorithm();

// stop and get the counter value
*DWT_CONTROL &= ~1;
clock_cycles_counter = *DWT_CYCCNT;

// print the counter value
printf("%d\n\r", clock_cycles_counter);

please suggest

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