PLLCFG on ARM7_LPC2129_IAR demo

Kernel
1

cra8000 wrote on Thursday, 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?

Regards
Carlos

2

rtel wrote on Friday, 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.

Regards.