topic Re: What's capacitor for oscillator? MC9S08LC36 in 8-bit Microcontrollers

What's capacitor for oscillator? MC9S08LC36

cicciounico — Thu, 22 Jan 2009 17:49:30 GMT

Hi,
I use MC9S08LC36 with oscillator at 2MHz.
I must use the micro at 3V but my Vcc can be less 3V (example 2.6V).
At 2.8V the oscillator don't run!
I suppose wrong capacitor (I have try 10pF and 18pF).
I have try to change ICGTRM but don't run!

It run only at 3V.
What's capacity I must insert with 2Mhz of oscillator?
Thanks

Added p/n to subject.

Message Edited by NLFSJ on 2009-01-22 08:55 AM

Re: What's capacitor for oscillator? MC9S08LC36

Lundin — Fri, 23 Jan 2009 18:43:50 GMT

I don't think this is related to the oscillator, and the cap values aren't all that critical. 18pF should work fine.

Instead I strongly suspect the low-voltage detection is reseting the circuit, as it should. This kicks at around 2.6V. Have you configured the LVD properly for lower voltages?

You should be able to easily determine if this is the problem or not, by checking the reset pin of the MCU with an oscilloscope.

Re: What's capacitor for oscillator? MC9S08LC36

cicciounico — Mon, 26 Jan 2009 21:34:07 GMT

Thanks!
The LVD is disable.
The reset is alwais high.
I have test my board with Vcc=2.8V and I have see XTAL (PTB1) alwais high. If I tap the pin of microcontroller with a finger the oscillator wakeup and it run then I suppose is the oscillator.
My supposition is wrong?
Vcc is not to low, is 2.8V.
Thanks again!

Re: What's capacitor for oscillator? MC9S08LC36

cicciounico — Tue, 27 Jan 2009 01:05:03 GMT

Now work!
I have change oscillator from 2MHz to 32KHz.
Now at 2.4V work fine and the oscillator run it.

thanks.