Hi,Originally posted in cdnusers.org by EngHan
The standard cell I am using does not have substrate and n-well tap, so
I have to placed well tape cell at regular interval in the core.
My perference is to use place them in checkerboard fashion. But I am
hit with what I believe is a limitation in the command addWellTap. It
is not easy to explain, so please be patience.
Let assume the max distance between the well tape is 40um (to simplify,
we ignore the width of the well tap and the height of the cell row). So
the command to add well tap should be:
addWellTap -cell wellTap -cellInterval 160 -checkBoard
The cell interal is 160um because a well tap can cover 40um on both
side. Also, in between the two cell taps on the same row, there are two
well tapes on the upper and lower row which are exactly in the middle.
Hence the spacing is 160um. The following drawing explain this:
(Note: X is the tie cell)
The problem occur when the upper or lower row is not available to place
the well tap cell (e.g. due to macro or placement blockage). In this
case, the tool shold place the well tie cell 160/4 or a max of 40um
away from the edge of the row. The tool now place it 160/2 or 80um
away. This is incorrect from my application of the command:
... Macro ... X
The distance marked "!" above is less than 160/2, but larger than 160/4. So an DRC will occur here.
Is there a workaround or hidden switch to get this command to work? Thanks.