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On Wed, Nov 28, 2007 at 03:32:27PM -0700, Bob Axtell wrote:
> Mike B wrote:
> > FYI
> >
> > In follow-up work on my clock board using the PIC internal oscillator, I varied the supply to my on-board regulator, and found the internal oscillator varies significantly. I did not think of doing this before, but I had some PS problems and with my counters set accurately to a 5V supply I varied the source from ~3V-15V and found the timing off by 50% to ~500%.
> >   
> 
> You got a PIC to work at 15V?
> > Not a huge suprise, but just some insight to consider if anyone else has timing issues. The internal RC appears more sensitive to supply than temperature. And since various designs affect the supply, you will also be changing your timing significantly.
> >
> >   
> Yes, I got similar results. It is NOT accurate enough for an RS232 
> serial port application; Microchip's adverts are not correct.

What was the other side of the serial hardware?


I've built a number of things using the internal osc and RS232 on
18f2520's and haven't had any problems when connected to good quality
FTDI-based usb to serial cables or on-motherboard RS232. Cheaper usb to
serial cables never seem to work however.


FWIW the power supply has always been 4.5V to 5.5V

- -- 
http://petertodd.org
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