2008-08-27 05:37:48     BF548 SCLK

2008-08-27 05:37:48     BF548 SCLK

Patrick Mc Donnell (IRELAND)

Message: 61170   

Hi,

If I set my VCO_MULT to 21 and SCLK_DIV to 4 and CCLK_DIV to 1 in my u-boot settings (ie edit u-boot/include/configs/bf548-ezkit.h) with my clock being 25MHz, am i right in thinking that my SCLK will now equal 131.25MHz?

Also if I set my VCO_MULT to 20 and SCLK_DIV to 4 and CCLK_DIV to 1 in my kernel settings

ie.

Blackfin Processor Options  --->

         Clock Settings  --->

                   [*] Re-program Clocks while Kernel boots?                                                                     

                   (20)  VCO Multiplier

                   (1)   Core Clock Divider (NEW)

                   (4)   System Clock Divider (NEW)

                   [ ]   Half ClockIn

                   [ ]   Bypass PLL

with my clock being 25MHz, am i right in thinking that my SCLK will now equal 125MHz?

Lastly, if i have both these settings which SCLK will my board use, the u-boot one or my kernel one?

Thanks,

Patrick

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2008-08-27 16:12:29     Re: BF548 SCLK

Mike Frysinger (UNITED STATES)

Message: 61190   

the clock algorithms are described in the HRM/PRM in many places.  the u-boot code as well describes it:

http://docs.blackfin.uclinux.org/doku.php?id=bootloaders:u-boot:porting

Core:   (CLKIN / (2 ^ CLKIN_HALF) * VCO_MULT) / CCLK_DIV

System: (CLKIN / (2 ^ CLKIN_HALF) * VCO_MULT) / SCLK_DIV