Instances

A cell is a reusable piece of layout. Placing a cell inside another cell creates an instance of it: the same geometry, drawn again somewhere else. In the GDSII output an instance is only a reference, so a cell placed a thousand times is still stored once.

cell Pad {
    layer metal {
        shape rect with 80um, 80um as body
        place body at self.origin
    }
}

cell Pair {
    place Pad at (0, 0)
    place Pad at (100um, 0)
}

Cells are placed outside layer blocks: directly in the cell, as above, or in a place { } block. Inside such a block the word place can be left out, which keeps long lists short:

place {
    Pad at (0, 0)
    Pad at (100um, 0)
}

Like a shape, a cell is placed by its origin here: Pad means Pad.origin. The next chapter shows the other anchors a cell can have. as names an instance — Pad at (0, 0) as left — so that other placements can refer to it.

A cell that no other cell places is a top cell. The preview shows the largest one.