> 1 50k resistor @ 39pf ceramic capacitor there was a long
> pause after 2 ON OFF cycle ( ON OFF ON OFF then a
> long PAUSE equal to the interval of 1 on or off ). contineously
> I then change the resistor to 10K... and this time a long PAUSE
> happens after 8 ON OFF cycle...

> I have reason to beleive that the code works correctly cause
> it turned on and off the LED as expected.. so this pauses must
> have something to do with  the resistor capasitor pair..

I'll be honest and say that sounds more like a code problem. I
can't see any reason why an RC oscillator should change like
that, and not so dramatically

> Is there a resistor capacitor pair that the microcontroller
> works reliably.. 

Microchip recommend (eg Fig 2-3 of 18Fxx2 datasheet) R
between 3k and 100k and C > 20pF

The measurements I made

http://home.clear.net.nz/pages/joecolquitt/0f84rc.html

show that the F84A, at least, can be run reliably at any speed from
almost 6MHz downwards

> I read somewher that there is an RC table values for different
> frequency in the datasheet but I could not find it for this particular
> PIC...

Because of the same R and C recommendations in the 18Fxx2
datasheet as in many, if not all, other datasheets, I think you
could assume that the RC oscillator is the same or similar in
every PIC

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