TMS570LC4357: How to test the time spent on this instruction “ asm volatile ("nop");”?

li xy

Part Number: TMS570LC4357

Hi all

I want to test the time cost When CPU run "__asm__ __volatile__ ("nop") " command.

In my mind, the nop command means empty instruction which means the time of CPU execute only one instruction, but how many cpu clock cycles does an instruction cycle take?

Can I get the real number like 10ns or ..?

Best Wish

over 1 year ago

0 Kowshik Gudimetla over 1 year ago

TI__Genius 15435 points

Hi li xy

The NOP command takes exactly one instruction cycle regardless of the processor. So, if you know the CPU frequency you calculate one instruction time by doing 1/Fcpu. Assuming core running at 400MHz the time taken to execute 1 NOP instruction is 1/400 x 10^6 = 2.5nS.

Hope this answers your query.

0 li xy over 1 year ago in reply to Kowshik Gudimetla

Intellectual 355 points

Thank you kowshik.

I have one more question. In my mind, I remember that one instruction cycle is more than one cpu cycles for other CPU.

What factors determine the length of an instruction cycle? Is CPU or ARM core?

+1 Kowshik Gudimetla over 1 year ago in reply to li xy

TI__Genius 15435 points

In my previous reply, when I meant 1 instruction cycle I meant NOP will take 1 CPU cycle. Apologies for that.

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TMS570LC4357: How to test the time spent on this instruction “ asm volatile ("nop");”?

Arm-based microcontrollers

Arm-based microcontrollers forum

TMS570LC4357: How to test the time spent on this instruction “ __asm__ __volatile__ ("nop");”?

TMS570LC4357: How to test the time spent on this instruction “ asm volatile ("nop");”?