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    • CommentAuthorshirly
    • CommentTimeMar 23rd 2014
     
    Hello,
    Sorry if this is kind of a basic question but i didnt get it.
    Do you recommend to work always with DBU of 0.001?how do i know the real size of shapes in microns?does the ruler shows the real size?
    By some reason i drow a whole layout with a DBU of 1e-5,do i need to fix it,and again how can i be sure what is the real sizes in micron?
    Thanks
    shirly
    • CommentAuthorMatthias
    • CommentTimeMar 24th 2014 edited
     

    Hi Shirly,

    the database unit is an internal unit and represents the finest grid you can draw a layout on. Your layout may be much bigger or drawn on a coarser grid, but the database unit is the very limit imposed by the file format. 1nm is a good compromise unless you work with very fine technologies that require a smaller resolution. KLayout will always show the real dimensions, except if you choose "show in database units" in the shape properties dialog for example.

    To change the database unit, just enter the desired new database unit in the database unit field in the save options. KLayout will take care to rewrite the shapes and cell instances to the new database unit. However, when you save to a bigger DBU or one that is not compatible with your layout design grid, snapping may occur and you should carefully check your layout for small gaps after that.

    Note, that if you change the database unit in "File/Layout Properties", the shapes and instance will not be rewritten and the layout will appear scaled after that.

    Matthias

    • CommentAuthorshirly
    • CommentTimeMar 25th 2014
     
    Hello Matthias
    Thanks for the answer.
    I have layout block of 10000um X12000um drawn in 1e-5 DBU.
    I try to make 10X10 array of this block,but it doesnt work.
    i can make only 2X2 array of this layout block.
    Any way to solve this out?
    thanks
    shirly
    • CommentAuthorMatthias
    • CommentTimeMar 25th 2014
     

    Hi Shirly,

    1e-5 is simply too small. GDS supports 32bit coordinates, that is roughly -2e9 to 2e9 database units. With 1e-5 micron, the layout area available is -20mm to 20mm. Change the database unit to 1e-4 for example (or even better, 1e-3) by saving your layout with that DBU and you will be able to create a 10x10 array.

    Matthias

    • CommentAuthorshirly
    • CommentTimeApr 2nd 2014
     
    Hello Matthias
    thanks,that helped me solving the problem.
    one small question-if i am changing the dbu of existing layout.do i need to add scaling factor in order to keep poligons in the same size?
    thanks
    shirly
    • CommentAuthorMatthias
    • CommentTimeApr 2nd 2014
     

    Hi Shirly,

    you just need to save the layout with a new database unit. Scaling is done automatically when you do so and the layout will look identical when you load it again.

    However, if you change the database unit in "Layout Properties", the shapes are not adjusted and therefore the layout will look differently afterwards.

    Matthias

    • CommentAuthorJSchoeck
    • CommentTimeJul 26th 2017
     
    Hi Matthias,
    sorry to resurrect this old thread, but I can't find a way to change the database unit any other way than with "Layout Properties". How do I "save the layout with a new DBU"?

    Also my default DBU is set to 0.01 µm and I don't know how to change it (and can't remember if I have done this myself a year ago or so).

    I can't find any insightful information on the forums.
    Thanks!
    Johannes
    • CommentAuthorMatthias
    • CommentTimeJul 26th 2017 edited
     

    Hi Johannes,

    Ok, it's a bit hidden ... to change it, go to the technology manager (Tools/Manage Technologies). Pick the "(Default)" technology and on the "General" page you'll find the default database unit value.

    The idea is to associate the database unit with a "technology" - because it's a physical design unit related to the feature size and needs to be aligned with libraries or upsteam tools you're using. In the broader sense, a KLayout "technology" is some setup you provide for layouting and the database unit is part of that.

    There is always one default technology, but you can have more than that. In this case, the default database unit will follow the technology definition when you create a new layout and chose a particular technology.

    Matthias

    • CommentAuthorJSchoeck
    • CommentTimeJul 27th 2017
     
    Thank you Matthias. I did specify a custom technology, but both that and the default have a DBU of 0.001 µm set.
    Still there is a preset of DBU 0.01 µm when I do File -> New Layout.

    I did find where this is saved and it's in the file "C:\Users\xxx\KLayout\klayoutrc", as are key-bindings etc.
    Maybe this information will help someone else (even though it's probably documented somewhere else, too ;) ).

    Best regards :)
    • CommentAuthorMatthias
    • CommentTimeJul 31st 2017
     

    Hi,

    Yes, the configuration file is one place. Only Linux the location is "~/.klayout/klayoutrc" ... but actually I can't confirm it does not change with the technology. When I edit the technology's DBU, the default will change ...

    What version are you using?

    Matthias