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[Piccolo] clock source


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As far as I understand, the Piccolos are usually run from an internal oscillator running at 10 MHz. They use a PLL to get to their actual SYSCLK (usually 50-80 MHz).

 

On the ISO controlCARD we are using, there is a 20 MHz crystal connected to X1 and X2, which I guess the internal oscillator uses to get a stable clock. Reading through the datasheets (man, there are a lot of them :D ) I wasn't really able to figure out how this works, if there are any registers to set etc. Can someone shed some light on this? I'm not talking about the PLL, SYS/BIOS takes care of that for me, but the clock sourcing.

 

Thanks!

TomKraut

Edited by bluehash
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Yes, you can use the the PLLCR register to set the clock ratio. Even before it goes to the PLL, you can divide the clock using the CLKIN divide options.

 

Clocking block diagram(pg 77 of the reference manual):

 

post-1-14264717199981_thumb.png

 

See pg 50 of the chip datasheet below. There are two documents you will need to reference. The chip datasheet and the family reference manual.

 

 

post-1-14264717199186_thumb.png

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