Hi Steve,
Thanks. Turns out it was user error. I had BSCTL1 set to DIVA1. Now that
should have given me 500us between pulses, but I was seeing 1ms. Setting
it to 0 got me to 250us tho. A bit strange. The 100kHz xtal calls for
the same caps as a 32kHz xtal.
Turning off the caps stopped the osc.
Steve Underwood wrote:
>
> Hi Garst,
>
> Did you turn off the 12pF caps in the MCU?
They are probably not the
> right thing for your 100kHz crystal. Also, what is your layout like?
Tons of ground plane.
> This oscillator is one of the lowest power consumers made to date, but
> the price is a little higher than usual sensitivity to layout. Make sure
> you have adequate ground plane around the crystal area. Run ground
> tracks around the two tracks from the crystal to the MCU. Be paranoid -
> it pays!
>
> Regards,
> Steve
>
> Garst R. Reese wrote:
>
> >Hi folks, I have a 100kHz LF xtal drivin ACLK, but the following setup
> >is giving me pulses spaced 1ms apart. Has anybody had any experience
> >trying to use a 100kHz xtal instead of the usual 32kHz? It looks like
> >I'm getting a subharmonic.
> >
> >Thanks,
> > Garst
> >void setup_timerA(void)
> >{
> > unsigned temp;
> >
> > #ifdef _SHOW_YELLOW_LED_
> > /*P1.6 is also connected to the IrDA CD pin*/
> > P1SEL |= BV(6);
> > P1DIR |= BV(6);
> >
> > #endif
> > //Assumes ACLK = 100kHz, MCLK = 3.6864MHz
> >
> > // set up timer A for 250us SAMPCON to ADC12
> > TACTL = TASSEL_ACLK + MC_UPTO_CCR0;// + ID_DIV8;
> > TACCR0 = 25; //RESET when TAR==CCR0
> > TACCR1 = 22; //SET when TAR==CCR1
> > TACCTL1 = OUTMOD_SET_RESET; //Mode 3: set_reset
> >
> > /*Start Timer*/
> > TACTL |= TACLR;
> > TACTL &= ~TACLR;
> >
> >}
> >
> >
>
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