abstract view for each layout view
Abstract views contain only the minimal data needed
for Place & Route
The use of abstract views instead of cell views enables smaller, more efficient design databases to be built and manipulated by P&R tools.
The abstract views do not contain underlying device details (poly, diffusion, n-wells, contacts).
They contain only the following:
- Outline of the cell (The “placement” tool places each cell in available sites in the core of the
chip. All the placer needs to know is the size and shape (outline) of the cell.)
- Pin locations and layer (Pins are usually metal connections to the underlying poly or diffusion
areas of the devices. The “router” tool uses these pin locations to route metal wires or connections
to each cell)
- Metal blockages (Areas in a cell where metal of a certain layer can not be routed because that
layer is being used in the full layout of the cell, but does not show up as a pin in the abstract view.
The example layout above is too simple to require blockages. These are more commonly needed in macro cells)
The layout and abstract views of all standard cells are built by a Library group. These cells are
usually initially built in a standard format called GDSII and then converted into tool-specific
formats (e.g. Milkyway database format for use by Synopsys tools).
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