Lpc2000

Hi Alejandro,

> I am Alejandro from Argentina.
> I am starting with 2138 uC.
> 
> I saw a sch from Jan Szymanski, I have a question for you.
> 
> You put a 560K resistor between the 32.768khz xtal and de uC.
> 
> Do you found that configuration in a Philips AN?
> 
> Can you explain it form me?
> 
> Best regards, 
> Alejandro

I haven't seen the schematic, but it is not uncommon for some oscillators to need a biasing resistor.
Basic crystal oscillators like these typically consist of a Pierce oscillatior.
A Pierce in silicon can be done with an inverting-gate style setup, or just a FET.
Depending on this, the oscillator circuit might need DC biasing to ensure it starts up reliably - 
therefore sometimes resistor between XIN and XOUT is used.
If you want to look closer at this, google for 'Pierce oscillator'. Should have lots of hits.

B rgds
Kris


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