Lpc2000

--- In lpc2000@yahoogroups.com, "Vimal Amin" <vimal19542000@y...> 
wrote:
>
> I need LPC2132 to run @32MHz for 2mSec (my time measurement periode)
> and then drop speed to 4MHz for 100mSec. This cycle continues
> forever. 
> Is it possible to change MSEL while running? I am afraid of Capture 
> range, Locking range and stabilizing period etc.
> 
> Anybody experianced with this?

Not reprogramming the PLL, but you can connect and disconnect it to 
switch between the crystal frequency and the PLL frequency.  This 
switching can be done instantaneously, when you just leave the PLL 
running all the time.  I have used this as a workaround for the old 
buggy bootloader on LPC2114 that didn't work at high cclk speeds.

Btw, the PLL input requires at least 10 MHz, so you can't go down to 
4 MHz.

SYS->PLLCON  = 0x01;  /* PLL = enabled, not connected */
SYS->PLLFEED = 0xAA;
SYS->PLLFEED = 0x55;

... running at slow Fosc speed

SYS->PLLCON  = 0x03;  /* PLL = enabled and connected */
SYS->PLLFEED = 0xAA;
SYS->PLLFEED = 0x55;

... running at full PLL speed


Karl Olsen