Updating from a higher level oe to a lower level
You do not have to declare all output pins as ports.
To specify signal attributes: Attributes specified for pins in a lower-level source are propagated up to the higher-level source.
Redundant nodes can later be removed from the designs during post-link optimization.
The following source fragment is an example of a lower-level interface statement.
The referencing of a logic description is called "instantiation." In a hierarchical design, you can't instantiate a top-level source from a source instantiated below that source.
You use hierarchy declarations in an upper-level ABEL-HDL source to refer to (instantiate) another ABEL-HDL source.