PIC 12 F 675 low power oscillator using 32,768MHz crystal

[RETFIE]

PIC 12 F 675 low power oscillator using 32,768 kHz crystal

Hello guys,

I am using low power oscillator configuration on PIC12F675 MCU with 32,768 kHz crystal.
My problem is that the program starts after approx. 12 sec from power supply switching on, what is too long time for me.
I am using 100pF capacitors on oscillator pins.
Does anybody have any idea to solve my problem please? Or is this starting time normal for this osc. type?

Thanks in advance

 

[colin55]

The chip has a start up delay of about 72mS via a separate RC oscillator.
Try your program with internal 4MHz osc and see if something your program is causing the delay.
Write a routine that turns on a LED immediately and compare the two oscillators.

 

[JimB]

Do you mean a 32.768 Mhz crystal, or a 32.768 khz crystal?
There is a big difference.

The PIC is only specified to a maximum 20Mhz clock frequency, so you are way over the top there.

Also, have you set the correct oscillator type in the configuration bits?

JimB

 

[MikeMl]

Haven't tried starting with an external crystal, but a 16F88 with an internal RC oscillator starts immediately on application of power.

I'm a retired CMOS chip designer, and I once designed a low power time-keeping chip (medical drug delivery device) that used a 32kHz crystal. It took many seconds for the oscillator to come up to full amplitude...

 

[Diver300]

The 100 pF capacitors are probably a bit large. However, 32.768 KHz watch crystals take several seconds to turn on.

If you are turning the device on and off, power consumption may not be so important. You could either run one of the other oscillators, (RC or high speed crystal) or you could star with that to begin with and then change to a slower one.

 

[colin55]

If you don't need accurate timing, just use external RC components to provide a low frequency.

 

[RETFIE]

I am sorry for my frequency mistake. I rewrote freq. from MHz to kHz.
Thanks to all for suggestions. Best Regards.

 

[blueroomelectronics]

Lower your caps, try 22pf

 

[RETFIE]

My problem was solved by changing capacitors to 47 pF.
Many thanks guys, regards.