At 12:22 PM 2/19/2006 -0700, you wrote:
>Olin Lathrop wrote:
>
> >Tomas Larsson wrote:
> >
> >
> >>Imperial is a pain in the arse, when it comes to PCB design.
> >>It seems that most editors has imperial units as base units in the
> >>database, and that creates round-off problem when working in metric.
> >>Since most Chip manufacturers is moving from imperial to metric it
> >>creates a problem.
> >>
> >>
> >
> >All CAD where I've looked into this use an integer representation that is a
> >sub-multiple of both mm and mil.
> >
> >
> >******************************************************************
> >Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
> >consultant in 2004 program year.  http://www.embedinc.com/products
> >
> >
>I've never encountered a rounding probem either , even good ole DOS Tango
>could go to .01 mm without any problems...
>
>Most genuine CAD programs use a very deep math unit
>
>--Bob

Real CAD (rather than the PCB variety) tends to use floating point math
with algorithms to detect when things are effectively in contact even if
the numbers are off by a bit.

The old, old EDA programs seemed to use integer units of mils, since they
crapped out at about +/-32" (16 bit representation).

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


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