Top

The layer is associated with the top surface.

For example, if a subcircuit is added to the top layer of a stackup, the subcircuit’s top-associated layers are mapped to the stackup’s top-associated layers. The subcircuit’s neither-associated layers are subsequently mapped to layers of the same type (e.g., signal to signal,) beginning at the top and moving downward.

If a subcircuit is added to the bottom layer of a stackup, this mapping is reversed; top-associated layers are mapped to bottom-associated layers and neither-associated layers are mapped to like layers, beginning at the bottom and moving upward.

Bottom

The layer is associated with the bottom surface.

For example, if a subcircuit is added to the top layer of a stackup, the subcircuit’s bottom-associated layers are mapped to the stackup’s bottom-associated layers. The subcircuit’s neither-associated layers are subsequently mapped to layers of the same type (e.g., signal to signal,) beginning at the top and moving downward.

If a subcircuit is added to the bottom layer of a stackup, this mapping is reversed; bottom-associated layers are mapped to top-associated layers. The subcircuit’s neither-associated layers are subsequently mapped to layers of the same type, beginning at the bottom and moving upward.

Neither

The layer is not associated with a top or bottom surface. Neither-associated layers are mapped to layers of the same type.

For example, if a subcircuit is added to the top layer of a stackup, the subcircuit’s neither-associated layers are mapped to layers of the same type (e.g., signal to signal,) beginning at the top and moving downward. If a subcircuit is added to the bottom layer of a stackup, this mapping is reversed; neither-associated layers are mapped to like layers, beginning at the bottom and moving upward.