MCU & FMI Clocks in special FIQ mode

jomedfree · ‎2009-12-10

Posted on December 10, 2009 at 18:32

jomedfree · ‎2011-05-17

Posted on May 17, 2011 at 09:59

I want to run my STR9 at 24MHz in normal mode and 96MHz in FIQ mode.

I have a 25MHz quartz, then tuned the PLL to 96MHz, set the RCLKDIV to 4 and activated the Special FIQ mode that switches the CPUCLK from RCLK (24MHz here) to fMSTR (96MHz here) during FIQ interrupts services.

I just do not understand what the FMICLK does.

In my case, FMICLK will be keeped at 24MHz during FIQ, is it a potential issue if the CPUCLK switches to 96MHz in the same time?

Will the CPU be fed from flash at 96 or 24 MHz?

Thanks in advance for any clarification, hope it may help the community...

tomas23 · ‎2011-05-17

Posted on May 17, 2011 at 09:59

The FMICLK follows the RCLK, so it will keep low freq. See the RM, clock tree and description of Special Interrupt mode.