Mike, The reference location for library parts in Protel is always
0,0 when you made the part. If the part is made offset from 0,0 you will notice that when you place the part you are moving it around by some point that was where 0,0 was relative to the footprint you designed in the library. Same for schematic symbols except that commonly you put the 0,0 reference just at the connection point of any pin. The issue with updating the part footprint is that if the references weren't the same for both versions of the footprint, the new footprint will come into your design at a location offset from the original and you will have to move it manually back into the desired location. If the offset is on some very small grid (multiples of 0.01 mils, 0.00001 inches), precise relocation of the new footprint could be nearly impossible but definitely frustrating.
Typically I design all SMT parts with 0,0 at the centroid pick location. Others design them such that pin one is the reference location (0,0). There is one caveat to using the pin one reference. Protel generates Pick n Place files with 3 coordinates, the reference location, the calculated center of all pads and the pin one location. With asymmetrical parts (DPAKS, TO263, TO252, etc.) Protel cannot calculate the correct center of the device based upon the pads because the pads are not centered within the part outline.
Protel does have an annoying habit of not refreshing the screen as much as they should. This is undoubtedly why you were seeing multiple pad locations onscreen. Just get used to using V, R (View Refresh) often while performing some operations. It is just second nature to me after years. If I pause slightly in my work, my immediate response is to hit V, R. Hold it, I just reread your response. Sounds like your refresh issue is something else. Could it be video card related? Protel hates the older (3 - 5 years) ATI cards. I thought it was the simple refresh issue when I first read it.
--
Sincerely,
Brad Velander
"mike" wrote in message
news:4191EC01.10107@netscape.net...
> Brad Velander wrote:
>
> Thanks for the input, I\'ll try it.
>
> I\'m not exactly sure what you mean by reference point. It\'s
currently
> pin 1. I am definitely going to have to move the origin and
introduce
> a .0025 mil error in one dimension to get all the pads exactly
on the 5
> mil grid in both axes.
>
> So far, I\'ve been unable to update the footprint. Seems that
refreshing
> the screen doesn\'t show the changes until I change to the next
part in
> the library then back to the one I\'m editing. Had pads six
deep from
> previous attempts to move stuff. Now that I know about the
quirk, I
> should be able to make it happen.
>
> I think it\'s definitely a printer...or in this case a plotter
problem.
> Plotter has 5mil resolution. Placement grid was 1mil, routing
grid was
> 16 mil for some unknown reason. The plotter is rounding the
coordinate
> to the nearest 5mil position. When you only have 5 mils
between traces,
> this is a disaster. I\'m hoping when I get everything
registered on a
> 5 mil grid, I\'ll be able to plot it...I hope.
>
> I\'m trying to plot this on copper to make the board.
Registration is
> critical. Sure wish I\'d figgered this out before I spent all
the time
> on the layout ;-)
> mike
>
> --