Lpc2000

Dear lpc group,
how can i program my lpc2148 to change the internal crystal oscillator 
frequency? 
One a first step I would like a 30Mhz (fosc and cclk) without pll 
enable. 
One second step,I would like tu have the most speed possible. I have 
deal with the pll (with the suppose of 14745600 Mhz), it's work with 
more speed but I think it can be better with other params like 5x12Mhz 
= 60Mhz. 
I have no switch on my board, so is there a register to subscribe the 
new frequency (fosc)or anything else to do?

Is there a way to control the actual frequency of the internal crystal 
oscillator?

Thanks for any help
Cyril

Hi Cyril,

I hope I'm not teaching you to suck eggs but...

There is no crystal inside the lpc2148.
A crystal is a tuned circuit. Inside a metal can.
You should have one or two on your test board.
When electrically "kicked" it rings at a certain frequency.
That frequency is very accurately determined by the
MECHANICAL properties of the crystal.
This frequency is printed on the outside of the crystal.

The lpc2xxx processor itself has little or no control
on the frequency.

If you want a different frequency from the crystal
then you buy a different crystal. Take off the old one
and fit your new one.

I happen to have a 10 MHz crystal for my lpc2292.
And a 12 MHz crystal for my lpc2148.

Why do you ask for 30 MHz _without_ the pll?
Both my 10 MHz and 12 MHz boards run the processor at 60 MHz.

Why do some people use 14.7456 (or whatever) MHz?
This divides exactly to many RS232 baud rates.
But the LPC2148 has a fractional baud rate divider so
you do not need exact division here.

 - Danish
--- In lpc2000@yahoogroups.com, "cyril_dunand" <dunand.c@...> wrote:

>
> Dear lpc group,
> how can i program my lpc2148 to change the internal crystal oscillator 
> frequency? 
> One a first step I would like a 30Mhz (fosc and cclk) without pll 
> enable. 
> One second step,I would like tu have the most speed possible. I have 
> deal with the pll (with the suppose of 14745600 Mhz), it's work with 
> more speed but I think it can be better with other params like 5x12Mhz 
> = 60Mhz. 
> I have no switch on my board, so is there a register to subscribe the 
> new frequency (fosc)or anything else to do?
> 
> Is there a way to control the actual frequency of the internal crystal 
> oscillator?
> 
> Thanks for any help
> Cyril
>