Lpc2000

Have you tried an oscilloscope to look at it?  Normally, you should see
a low voltage signal - a sine wave about 1Vpp at 32K.

 

If no signal...

-          swap in the crystal from your demo board

-          swap in the caps from the demo board 

-          check for shorts in the crystal circuit.

 

 

You are right - the internal structure of the circuit is basically just
an inverter - the output the input both go to the cap. The ends of the
crystal also go thru the caps to ground (the tank circuit)  See the data
sheet for details.   Three external parts.  So you either have the
circuit wrong, board laid out wrong, the wrong parts, or defective parts
- this is very simple circuit

 

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From: lpc2000@yahoogroups.com [mailto:lpc2000@yahoogroups.com] On Behalf
Of r_bottleneck
Sent: Wednesday, November 30, 2005 11:04 PM
To: lpc2000@yahoogroups.com
Subject: [lpc2000] Re: RTC problem

 


Hello,

I still have the problem that the RTC is not working on my new board.
However, I found,  the RTC is working with internal clock, in opposite 
I mentioned in my start message. So there must be a problem with the
32Khz oscillator internally or externally.

I can not swap the LPC2138, because I have just a single board and
I dont want to kill it while un-soldering the CPU.

Is it possible to do a basic test to check if the oscillator is ok ? 
I mean it must be something like an inverter and there is an input and
output pin.

Does anbody know how the oscillator of the LPC2138 internally looks 
like? 

What can prevent the 32kHz oscillator from working internally?

Thanks






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