Crystal osc running but PIC not using it

[p15218]

I'm trying to use the PBP Count function with a bit more stability than the 16F690's internal RC oscillator provides.

My problem is that I have the crystal oscillator running with the following edit to 16f690.inc file:
; __config _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_ON & _CP_OFF ------- original code
__config _HS_OSC & _WDT_ON & _MCLRE_ON & _CP_OFF --------my edit

BUT it matters not if I remove or short the crystal, the code still runs!
I've checked the 4 MHz crystal's pins with a scope & counter and it is active at about 3999990 Hz, close enough to 4 MHz for me.
MCLR is pulled high with a 4.7k Ohm resistor.

What else do I have to do to enable the crystal oscillator internal to the PIC ?
thanks
Bob

[Charles Linquis]

Your problem lies with the line

__config _INTRC_OSC_NOCLKOUT

The "_INTC_OSC" part means to use the internal oscillator.

You should change this to "_XT_OSC" instead

[p15218]

Your problem lies with the line

__config _INTRC_OSC_NOCLKOUT

The "_INTC_OSC" part means to use the internal oscillator.

You should change this to "_XT_OSC" instead

Well thanks but I did...notice the ";" commenting the "_INTC_OSC" line out.
Changing to "_XT_OSC" has activity at the crystal as well as _HS_OSC did with the same result that pulling the crystal makes no difference, the code runs no matter.

[Darrel Taylor]

Make sure your programmer is updating the CONFIG settings of the chip.
Usually there's an option for that.

It may still be using the CONFIG settings from a previous program.
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[Archangel]

Hi Bob,
This particular PIC has special Oscillator, options and Has FSCM, which stands for Fail Safe Clock Monitor - datasheet page 49 of 294 and as I understand it, it automaticly deploys an internal clock when oscillator failure occurs, pretty darn nifty feature unless you are doing what You want to . Easiest way is use a cheaper PIC.

[mister_e]

Easiest way is use a cheaper PIC.

And never learn... not for me.

[Archangel]

And never learn... not for me.

Me no understand . . . was I wrong?

[mister_e]

may bee hi deed not reed care foolee dee hole tred

'The Easiest solution and use another PIC' reply always drive me nuts when the user don't need to and have a nice 'learning opportunitie' on hand... i know i may have badly interpret it anyways... Need to sleep... sorry

Good news, you are right! Assuming the Fail-Safe clock monitor AND the int-ext-switchover mode are both enable, at POR, the internal OSC run @ 4MHz.... hence why it always work without noticeable bugs.

[p15218]

Ah, thanks to Joe S. for the info. I have verified this by using a 4.91 Mhz crystal, far enough out to show errors in frequency counting.
Pulling the crystal had the PIC instantly switch to it's internal RC source. THANKS!
Bob

[Archangel]

may bee hi deed not reed care foolee dee hole tred

'The Easiest solution and use another PIC' reply always drive me nuts when the user don't need to and have a nice 'learning opportunitie' on hand... .

ICE e e e e gotit EWE SCAERT MEE . . thought I missed something in de datasheet, possible as it was about 4 am here when I wrote that. HE HE You don't miss very many MASTER_E, I humble grasshopper, wish, only to learn . . .