Florent Patinote

Problem with instruction executing timing

Discussion created by Florent Patinote on Aug 17, 2009
Latest reply on Aug 20, 2009 by Oliver Betz



I have done a little program to verify my instruction executing timing.


My program is composed of :

-Set an output

-Reset the same output

-Increase an integer variable (6times)

-Set the output


I capture my output an logical analyser.

The time for execute this program (47 processor cycles between the set and the reset) is about 1,975us. That mean one cycle timing is about 42ns. That done about 24Misps, in the data sheet it's write 56Misps.

I don't understand why I haven't the better performance because I use an external oscillator at 25Mhz like the Evaluation board (MCF25535EVB) and the MCF initialisation is the same.


I have check all the register and is good. Anybody have an idea?