68300

Thanks to Charlie!
In my start up code for the clock (SYNCR) I had X bit = 0. A no-no @  
20.45 MHz.
Changed the SYNCR value as per Charlie's recommendation and the clock  
is now stable over temperature. Thanks again Charlie !
New problem! I have a choice of either 19.92 MHz or 20.97 MHz. Either  
breaks my CAN communication. I'm running at 250 kbit/s. and I need to  
communicate with SJA1000 CAN devices and 56F803 Freescale devices.
Anyone with CAN values that they would recommend?

On Jun 3, 2005, at 10:49 AM, Tim wrote:

> Hello Group ( I hope there are people still out there ),
>
> I have an issue with clock drift with temperature. I have a -20 to
> +60C 4.194 MHz crystal on a 68376 design. As I get the temperature up
> to about 50 C, I start to see the CLKOUT pin frequency drop. The
> normal rate is 20.45 MHz (picked for CAN reasons)
> At about 50C clock out is 20.09 MHz , at 60 C -> 19.63 MHz.
> This more than +/- 50 ppm spec of the crystal.
> I am using a 1.5 K ohm series resistor and 22 pF load caps. I have
> tried 27 pF as well.
> I am using the high stability VCO filter too.
>
> Anyone have some pointers as to how to correct this?
>
>
>


Tim Flynn
RMS Welding Systems
Ph.(780)955-3907
http://www.rmsweldingsystems.com



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