I use guard rings when I can... the crystal and 2 caps are all within =20
the guarded area, and the guard looks like a wide anchor with the =20
outer arcs going around the caps and crystal.  In Eagle, I create =20
these in the following order:

- Manually create guard traces (using a different net name),
- Manually route anything else necessary,
- Autoroute all else,
- Change the name of the guard trace to Gnd or Vss as required and it =20
will create a connection.
- Manually route the new ground connection (ensuring there is no =20
current path *through* the outer guard areas).

Cheers,
-Neil.





Quoting Harrison Cooper <HCooper@fusionio.com>:

> I believe you can break up the ground pour (make an island) by =20
> drawing in lines on the restrict layer..be it bottom or top.  If you =20
> make a complete isolated island you will need to tie it with a via =20
> to another layer with the same signal else when you do the =20
> pour..nothing will be there since there isn't an attached net.
>
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On =20
> Behalf Of Lee Mulvogue
> Sent: Wednesday, April 18, 2012 11:18 PM
> To: piclist@mit.edu
> Subject: [PIC] Do you use isolated GND pour for osc?
>
>
>
> 	Hi all, I'm laying out my first "pro-quality" PCB with a PIC24FJ64, =20
> and have run into a little issue, but don't know if it's actually an =20
> issue or not.
>
> 	In the spec sheet under External Oscillator Pins, it goes into =20
> great detail about creating an isolating GND pour around the OSC, =20
> and that this pour should be a separate entity from the "normal" GND =20
> pour that many (most?) use across the whole PCB.  I've created this =20
> isolating pour top and bottom, but I seem to have a problem with =20
> Eagle PCB in that I seem to only be able to create one "GND" polygon =20
> per layer, so can't do an isolation pour as well as a pour for the =20
> rest of the board.  Haven't found any threads on this topic elsewhere.
>
> 	But the thing is, in any pictures I've found online of PIC-based =20
> PCBs, no-one seems to actually be doing this isolating "ring".  So =20
> is it really something I should be concerning myself with?  Or =20
> ideally, does anyone know a way of geting multiple "GND"-named =20
> polygons on a layer in Eagle?
>
> 	Thanks for any input
>
> 	Lee
>
> -------------------------
> Msg sent via Webmail - http://hosting.myob.com/
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