Greetings,

    Just got confused with DCO specs and XTAL usage. I read in 
MSP430F149 datasheet that it supports 8Mhz a external HF XTal. Is it 
possible to archive the same speed using DCO with the LF 32kHz XTAL? 
The maximum MCLK I got was 4.8Mhz on my system.


Gabriel

>     Just got confused with DCO specs and XTAL usage. I read in 
> MSP430F149 datasheet that it supports 8Mhz a
external HF XTal. Is 
it 
> possible to archive the same speed using DCO with
the LF 32kHz 
XTAL? 
> The maximum MCLK I got was 4.8Mhz on my system.

According to the datasheet SLAS272C, the max DCO frequency f(DCO77) 
is 4.4/4.9/5.4MHz min/nom/max @ 3.0V.
So you can't get MCLK higher than this if you use the DCO as clock 
source.

Wolfgang

I thought I remembered that you could if you used an external injector
resistor...

--Bruce

> >     Just got confused with DCO specs and XTAL
usage. I read in
> > MSP430F149 datasheet that it supports 8Mhz a external HF XTal. Is
> it
> > possible to archive the same speed using DCO with the LF 32kHz
> XTAL?
> > The maximum MCLK I got was 4.8Mhz on my system.
>
> According to the datasheet SLAS272C, the max DCO frequency f(DCO77)
> is 4.4/4.9/5.4MHz min/nom/max @ 3.0V.
> So you can't get MCLK higher than this if you use the DCO as clock
> source.
>
> Wolfgang

Hi,

> Just got confused with DCO specs and XTAL usage. I
read in
> MSP430F149 datasheet that it supports 8Mhz a external HF XTal. Is it
> possible to archive the same speed using DCO with the LF 32kHz XTAL?
> The maximum MCLK I got was 4.8Mhz on my system.

yes, you can measure MCLK with the LF XTAL and dynamically you can modify MCLK
by dividing.
I've seen an application note or something like that from TI. I don't
remember where but it should
be easy.

Regards

Rolf F.

The DCO will only go up to about 5MHz using the internal current setting
resistor. It can go faster but you need to connect external resistor Rosc.
This also has the advantage of being much more temperature stable than the
internal resistor. You can implement a software Frequency Locked Loop to
further stabilise the DCO using the 32kHz xtal as a reference. This is
covered in app notes on the TI site.

Cheers,
Kevin Brewster
Australia

> Just got confused with DCO specs and XTAL usage. I
read in
> MSP430F149 datasheet that it supports 8Mhz a external HF XTal. Is it
> possible to archive the same speed using DCO with the LF 32kHz XTAL?
> The maximum MCLK I got was 4.8Mhz on my system.

Hi,

    Thank everyone for all answers. However, since I'll use only one 
mclk frequency (I won't dynamically change it or anything else), is it a 
good idea to use the 32kHz XTAL + externa Rosc + DCO and FLL routines? 
Wouldn't be much easier (and probably costs about the same) to use only 
a HF XTAL?

Gabriel,

Kevin Brewster wrote:

> The DCO will only go up to about 5MHz using the
internal current setting
> resistor. It can go faster but you need to connect external resistor Rosc.
> This also has the advantage of being much more temperature stable than the
> internal resistor. You can implement a software Frequency Locked Loop to
> further stabilise the DCO using the 32kHz xtal as a reference. This is
> covered in app notes on the TI site.
>
> Cheers,
> Kevin Brewster
> Australia
>
> > Just got confused with DCO specs and XTAL usage. I read in
> > MSP430F149 datasheet that it supports 8Mhz a external HF XTal. Is it
> > possible to archive the same speed using DCO with the LF 32kHz XTAL?
> > The maximum MCLK I got was 4.8Mhz on my system.
>
>
>
> 
>
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