How many nanoseconds a NOP consumes at 32MHz stm32L152re?

[Vasile Guta_Ciucur]

Posted on October 30, 2017 at 01:05

Thank you in advance!

[Tesla DeLorean]

Posted on October 30, 2017 at 02:10

You can measure instruction cycles with DWT_CYCCNT

[Vasile Guta_Ciucur]

Posted on October 30, 2017 at 11:59

Ah, something like this:

uint32_t cycles = 0;
/* DWT struct is defined inside the core_cm4.h file */
DWT->CTRL |= 1 ; // enable the counter
DWT->CYCCNT = 0; // reset the counter
delayUS(1); // <-- here my Nop()
cycles = DWT->CYCCNT;
cycles--; /* We subtract the cycle used to transfer 
 CYCCNT content to cycles variable */�?�?�?�?�?�?�?�?�?

Carmine Noviello tutorial

https://www.carminenoviello.com/2015/09/04/precisely-measure-microseconds-stm32/

[RomainR.]

Posted on October 30, 2017 at 13:15

Hello,

It takes 1 cpu cycle count. maybe 31,25ns. See 

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0337h/CHDDIGAC.html

 

Also the assembler generates alternative instruction which does nothing, such mov r0, r0

Regards