Cycle counter on ARM Cortex M4 (or M3)?

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I'm trying to profile a C function (which is called from an interrupt, but I can extract it and profile it elsewhere) on a Cortex M4.

What are the possibilities to count the number of cycles typically used in this function ? Function shall run in ~4000 cycles top, so RTC isn't an option I guess, and manually counting cycles from disassembly can be painful - and only useful if averaged because I'd like to profile on a typical stream with typical flash / memory usage pattern.

I have heard about cycle counter registers and MRC instructions, but they seem to be available for A8/11. I haven't seen such instructions in cortex-Mx micros.

cortex-m3 arm embedded
5 Answers

This is just easier:

[code]

#define start_timer()    *((volatile uint32_t*)0xE0001000) = 0x40000001  // Enable CYCCNT register
#define stop_timer()   *((volatile uint32_t*)0xE0001000) = 0x40000000  // Disable CYCCNT register
#define get_timer()   *((volatile uint32_t*)0xE0001004)               // Get value from CYCCNT register

/***********
* How to use:
*       uint32_t it1, it2;      // start and stop flag                                             

        start_timer();          // start the timer.
        it1 = get_timer();      // store current cycle-count in a local

        // do something

        it2 = get_timer() - it1;    // Derive the cycle-count difference
        stop_timer();               // If timer is not needed any more, stop

print_int(it2);                 // Display the difference
****/

[/code]

Works on Cortex M4: STM32F407VGT on a CJMCU Board and just counts the required cycles.

user_71303510
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