Correct way to use Components?

Speaking of Incremental Compilation, that's also why I don't like internal tri-states. Sure, they are convenient when multiplexing data from numerous hierarchies onto an internal bus without routing all the data signals to a common point and multiplexing explicitly.

However, you can easily partition a design in a way that triggers on error in Quartus II. For example, if your internal bus feeds partition boundary output or inout, then the tool creates an I/O driver, thinking you're possibly describing an actual top-level pin with tri-state behavior. It can't simply look up in the hierarchy for a top-level pin connection because that wouldn't be an incremental flow - you can't make synthesis decisions using information from other partitions, which should be able to vary independently. Or what if you tri-state bus is split across partition boundaries? Not exactly fun times, let me tell you from experience. :)

I imagine all tools have quirks in supporting internal tri-states.