If this topic was previously mentioned, I apologize for not finding it.

I'm using a 16F877A with a 4 MHz crystal and two 22pf caps with a LED hooked up to portb.1 and the code from example 2 of DT_ints-14.bas on DTs site. I'm using a oscope to look at the timing of the LED flashes and they are occuring around 950msec apart.

My question is, is there a way to tune the oscillator or modify DT interrupts to get it closer to a true 1 second pulse time? I know it's not far off but I was trying to learn something and maybe make it more accurate at the same time. Your help would be appreciated.

Yes I did read the datasheet but I couldn't find anything like OSC tune that I've seen for the 12F683.