Clock cycles

Hi all:

I have been stuck on this problem for a while - can someone help me figure this out? For the following instruction, the instruction set manual says it should take 5 clock cycles, whereas according to my measurements using an oscilloscope, I should get 4 clock cycles. What could be the reason for the difference? I am using TelosB.

add #1, -4(r4)

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You don't say what processor.

If it's pipelined, it's going to be hard to assign a one-and-only number of clock cycles, because the number taken will depend on _everything_.

Tim Wescott 
Wescott Design Services 
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Reply to
Tim Wescott

How are you measuring its execution time?

Have you tried: add #9, -4(r4) and: add #1, -12(r4)

Reply to
Don Y

The TelosB data sheet says that the processor is a MSP430 8 MHz.


Reply to
Tauno Voipio

Op Fri, 24 Feb 2017 14:52:51 +0100 schreef arshadnatasha :

Have you measured other instructions, like NOP?

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Reply to
Boudewijn Dijkstra

This exercise totally baffles me. How can you precisely and directly measure a single instruction execution time? There are numerous ways to indirectly measure it and calculate a probable mean.


Reply to
John Speth

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