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Other CAD Tools >> Entry Tools >> How to set snapgrid less than a quarter grid
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Message started by rf-design on Jan 15^th, 2010, 3:59pm

Title: How to set snapgrid less than a quarter grid
Post by rf-design on Jan 15^th, 2010, 3:59pm

The default minor grid setting is 0.125 and 0.0625 for the snapgrid. If I set the snapgrid to 0.03125 I could snap to 4 grid points for each displayed minor grid. If I set the snapgrid to 0.015625 I get an other snapgrid which is not submultiply of the minor grid.

First I wonder why I could enter every floating. Second why an entered floating for the snapgrid is not rounded to the next submultiply of the minor grid. So and what happen if I edit with this alien grid. Issue exist in 5.4 and 6.1.

Title: Re: How to set snapgrid less than a quarter grid
Post by Andrew Beckett on Jan 16^th, 2010, 9:45am

The default DBUperUU (Database Unit per User Unit) for schematics and symbols is 160, and the User Unit is an Inch. So this means the database resolution is 1/160 inch, i.e. 0.00625. The actual database is stored using integers.

So this means that 0.03125 is represented with 5 database units. If you were to use half that, it would need 2.5 database units - and since they are integers, it will be either 2 or 3. So this will explain the anomaly, I think.

You didn't actually say which view you were talking about, or even which tools you were talking about. I'm guessing you're talking about Virtuoso Schematic Editor - but you really should be more specific when you post - not everyone in this forum is using Cadence tools.

Best Regards,

Andrew.

Title: Re: How to set snapgrid less than a quarter grid
Post by rf-design on Feb 1^st, 2010, 6:50pm

Sorry I mean Cadence Symbol Editor 4.4.6 5.1.4 & 6.1.3

As I understand the DBUperUU only define the scale factor if there is a needed relation to a physical size like paper sheet size. I also understand that the coordinates of the symbol should be restricted to a integer grid.

So but what happen if I change the grid setting. I found that if I change the setting that the new snap grid points are outside of the previous sketched graphics. Further smaller settings of the snap grid are not executed correctly.

So if I want to draw on a more fine grid I have to change the DBUperUU from 160 to 320? Are then all schematic symbols are rescaled by a integer factor 2 or are they getting smaller?

Title: Re: How to set snapgrid less than a quarter grid
Post by Andrew Beckett on Feb 2^nd, 2010, 10:25pm

Yes, if you want a finer grid, you'd need a larger DBUperUU, as I explained before.

And if you do that, any existing symbols will end up half the size. So that's not a decision you want to take lightly!

Regards,

Andrew.