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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.
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The Cortex-M3 and Cortex-M4 are very similar cores. Each offers a performance of 1.25 DMIPS/MHz with a 3-stage pipeline, multiple 32-bit busses, clock speeds up to 200 MHz and very efficient debug options. The significant difference is the Cortex-M4 core's capability for DSP.
The Cortex-M3 processor is specifically developed for high-performance, low-cost platforms for a broad range of devices including microcontrollers, automotive body systems, industrial control systems and wireless networking and sensors.
The Arm Cortex-M4 processor is a highly-efficient embedded processor. The Cortex-M4 processor is developed to address digital signal control markets that demand an efficient, easy-to-use blend of control and signal processing capabilities.
ARM Cortex-M3 system tick timer, including an external clock input option. Low power RTC with a separate power domain and dedicated oscillator. Standard JTAG test/debug interface for compatibility with existing tools. Crystal oscillator with an operating range of 1 MHz to 25 MHz.
Take a look at the DWT_CYCCNT register defined here. Note that this register is implementation-dependent. Who is the chip vendor? I know the STM32 implementation offers this set of registers.
This post provides instructions for using the DWT Cycle Counter Register for timing. (See the post form 11 December 2009 - 06:29 PM)
This Stack overflow post is an example on how to DWT_CYCCNT as well.
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