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PLLCFG on ARM7_LPC2129_IAR demo

Posted by cra8000 on July 16, 2009
Hi all,

It's correct PLLCFG on ARM7_LPC2129_IAR demo or must be PLLCFG = 0x24 ?

On FreeRtos 5.4.0 demo project:
Fosc : 12Mhz
CCLK : 60Mhz
PLLCFG = 0x04

If it's not correct there's a big problem?


RE: PLLCFG on ARM7_LPC2129_IAR demo

Posted by Richard on July 17, 2009
The PLL output frequency is given by:

Fcco = Fosc * M * 2 * P

which given the value 0x24 in PLLCFG gives:

120MHz = 12000000 * 5 * 2 * 1

which would indeed appear to be wrong, but the demo seems to run at the right frequency which must be fluke.


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