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Problem in viewing grid during Layout

Jithin

Sir/Madam,

 I have been using Cadence Virtuoso 6.1.3.1 and the process chosen is 65nm CMOS .  While trying to Layout a design it is found that the grid is not visible but if we zoom till only one transistor, the grids become visible. My querry is Is there any issue if grid is not visible while doing Layout? or if its a problem then how can I make the grid visible.

The values given in the display  tab are given below

Minor Spacing: 0.01

Major Spacing : 0.05

X Snap spacing: 0.005

Y Snap Spacing: 0.005

Thanks and Regards

 Jithin K 

 

  •  Hi Jithin,

     

    the visible gridpoints spacing is controlled by the "Minor Spacing" and "Major Spacing" parameter.Depending on their value they will not be displayed if you zoom out too far, there would be simply too many of them to help you in any way and they would obscure your view. So you need to increase their value till it fits your needs. I would increase the major/minor value ratio to something around 10 or higher to be usefull.

    Don't play around with the x/y Snap Spacing. That's your actual drawing grid into which all your objects need to fit. If you have that wrong you will get flooded with DRC errors and the layout can't be processed by your maskshop.

     

    Regards,

    Marc

     

  • Sir, Even after keeping the ratio of major to minor spacing to 10, I was not able to see the grid without zooming. But when I zoom to a particular level the grid began to visible and the minor and major spacing seems to be exact as given the respective tabs. So is it because of the deep sub micron technology using I was unable to see the grid when I opened the Layout window with out any zooming. And also how should we configure the X-snap and Y-snap spacing. Thanking for your reply. Regards, Jithin K

  • Hi Jithin,

    As Marc stated, the grid value and zoom level affect whether or not the minor dots will be displayed; these should not be confused with the X and Y snap spacing values, though typically you would pick values that work together.

    Are you able to move to the IC615 release or newer since Virtuoso introduced functionality that better allows for "high altitude" editing, such as the smart snapping feature (for example the ruler can be placed and accurately snapped to edges that would otherwise require the user to zoom in).

    Regards,

    Lawrence.

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