Creating delay using __asm__("nop")

[MGado.1]

How to measure the time from __asm__("nop") on STM32F730 using 216 MHz clock? I did try to check it using osciloscope without success. The time is bigger than 1/216 MHz.

[TDK]

DWT->CYCCNT will measure ticks. You'll need to figure out and subtract off the overhead for accessing it.

https://community.arm.com/developer/ip-products/processors/f/cortex-m-forum/8952/where-to-find-the-execution-cycles-of-cortex-m7-instruction

The Cortex-M7 pipeline is not as straightforward as it is for Cortex-M4. NOP instruction isn't guaranteed to take any time at all.

[Tesla DeLorean]

Why would you do it this way? Seems highly prone to caching and superscalar issues, not to mention interrupts.

Can't you use a 32-bit TIM to account for passage of time, or use the DWT_CYCCNT to count cycles?

[Tesla DeLorean]

volatile unsigned int *DWT_CYCCNT = (volatile unsigned int *)0xE0001004; //address of the register

volatile unsigned int *DWT_CONTROL = (volatile unsigned int *)0xE0001000; //address of the register

volatile unsigned int *DWT_LAR  = (volatile unsigned int *)0xE0001FB0; //address of the register

volatile unsigned int *SCB_DEMCR = (volatile unsigned int *)0xE000EDFC; //address of the register

 *SCB_DEMCR |= 0x01000000;

 *DWT_LAR = 0xC5ACCE55; // unlock

 *DWT_CYCCNT = 0; // reset the counter

 *DWT_CONTROL |= 1 ; // enable the counter

uint32_t start, finish, delta;

start = *DWT_CYCCNT;

...

finish = *DWT_CYCCNT;

delta = (finish - start);