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No-grid errors with power and ground rail in Encounter

Alexsoton

 Hello,

In Encounter, I click and highlight Pref Track on the side toolbar to see the routing grid. I don't know why there is always a half grid in both the bottom and left edges of the die. What do you guys say about it? Isn't it wierd? Also, as a result of that, my core boundary edge lies in the middle of two grid line, rather than overlaps with one grid line. This further causes no-grid DRC errors with my power stripes, since the centers of the power stripes are now not on the grid line but in the middle of two grid line.  

Thank you. 

Alex

Parents

  •  Hi Alex,

    This is actually completely normal. The default is to start the grid at a half-grid offset from the core. You can change this if you really want to with the OFFSET line for each metal layer in the tech LEF. However, most std cell libraries are set up so that with this half-grid offset, the pins will line up on grid. If that's not the case for your library, then changing the OFFSET should do the trick.

    As long as your power stripes are legal on the MANUFACTURING grid, then it's not really illegal to have them off the routing grid. However, you could be wasting routing tracks by having them this way. It is recommended to center power stripes on routing grids.

    Finally, nanoroute can route well to offgrid pins. But if your whole library is this way, then you may see some issues - long run time, more DRCs, etc. Make sure your std cell pins are on grid, and then if  you have some macros with offgrid pins, you'll still be fine.

    - Kari

Reply

  •  Hi Alex,

    This is actually completely normal. The default is to start the grid at a half-grid offset from the core. You can change this if you really want to with the OFFSET line for each metal layer in the tech LEF. However, most std cell libraries are set up so that with this half-grid offset, the pins will line up on grid. If that's not the case for your library, then changing the OFFSET should do the trick.

    As long as your power stripes are legal on the MANUFACTURING grid, then it's not really illegal to have them off the routing grid. However, you could be wasting routing tracks by having them this way. It is recommended to center power stripes on routing grids.

    Finally, nanoroute can route well to offgrid pins. But if your whole library is this way, then you may see some issues - long run time, more DRCs, etc. Make sure your std cell pins are on grid, and then if  you have some macros with offgrid pins, you'll still be fine.

    - Kari

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