I've recently started using the internal oscillator to run my 16F88
projects when timing is not super-critical.  Yesterday, I was tinkering
with a PWM fan controller using TMR0 w/out prescaler to generate
interrupts every 128uS (8MHz internal clock).  256 interrupts
constitutes one full PWM period (32.768mS).  When checking the period
with a frequency counter, I noticed allot of jitter in the period
length.  Since TMR0 is not reloaded, I expected the interrupts to be
perfectly spaced.  I reprogrammed the chip using INTRC_CLKOUT so I could
check the frequency.  What I found was quite surprising to me.  While
overall the INTOSC stays within it's 1% spec, in the short run the
frequency (2MHz CLKOUT) varies by several kHz continuously.  I tried a
different chip and got the same results.  Is this typical of the
internal oscillators?  The power supply is stable and regulated.

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist