Harold Hallikainen wrote:

>I'm working on a project right now where I run the output of the PIC
>oscillator (8 MHz) from one side of the resonator to a couple Maxim SPI
>UARTs. I see no evidence of loading the oscillator.
>
>  
>
A word of warning: Maxim only makes two SPI uarts. Be aware that the 
only problem I had
with them is accidentally overdriving the crystal input. The problem was 
not noticeable until
writing the code. The  clock in the pic was skipping cycles. I'd reserve 
space for a resistor
before each Maxim UART  osc input. I was using a commercial oscillator, 
and had to use
220-470 ohm resistors to knock the drive level down.

If you use the one with built-in RS232 level drivers, it needs a 
tantalum 10uF very close to
VCC and GND pins.

Once you fix that, those uarts work very well.
 

>In another project, I used a dual varactor as the load capacitors on a
>crystal on a PIC oscillator. The output side of the oscillator goes
>through a 10k resistor to an op amp voltage follower to a BNC on the front
>panel. This allows the user to adjust the PIC oscillator frequency to
>exactly 10MHz. This also seems to have worked fine.
>
>Harold
>
>
>  
>

--Bob

-- 
Note: Attachments must be sent to
 attach@engineer.cotse.net, and 
 MAY delay replies to this message.
        520-219-2363

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