Running at 96 MHZ

[jonny_bee_henry]

Posted on February 11, 2008 at 11:19

Running at 96 MHZ

[jonny_bee_henry]

Posted on May 17, 2011 at 09:31

We're evaluating the IAR quick start kit which comes with the STR912-sk board with a STR912FW4X cpu. X-tal is running at 25MHZ. When we try to use the PLL to bump the clock rate up to the rated 96MHZ, we seem to break down at speeds above 60-70MHZ.

(SCU_PLLFactorsConfig(48, 25, 1) works,

(SCU_PLLFactorsConfig(66, 25, 1) works,

(SCU_PLLFactorsConfig(72, 25, 1) stops working

Any suggestions? does the prt actually work at 96MHZ?

[anis]

Posted on May 17, 2011 at 09:31

Hi Jonny_h,

You must ensure that the PLL factors M, N and P respect the conditions indicated in reference manual (see PLL paragraph 2.4.8)

In order to have 96MHz, please use the following values:

N= 192 , M= 25 and P = 2.

Also you must set the flash read wait states to 2 in order to execute from flash.

Best Regards,

STARM

[jonny_bee_henry]

Posted on May 17, 2011 at 09:31

Thanks,

Is the requirement for 2 flash read wait states when running at 96MHZ documented anywhere?

[anis]

Posted on May 17, 2011 at 09:31

You can find this information in the STR9 flash programming manual ( see Flash Configuration Register p32)

I agree with you, this info should be more visible in the reference manual.

Best Regards,

STARM

[jonny_bee_henry]

Posted on May 17, 2011 at 09:31

Thanks...

[mbalvert]

Posted on May 17, 2011 at 09:31

Update: Page 23.. it is.