The Tower System is a simple concept. Take basic hardware modules, connect them together and start designing. There are two types of hardware modules, MCU/MPU and peripheral (i.e. serial, memory, LCD, etc.), which plug into backplane "elevator" boards. The Tower System supports up to four prototyping boards. The boards are installed into one of the slots in the Tower System, the signals from each installed module are shared between modules and made easily accessible through exterior headers on the Tower System.
For an overview of the Tower System and some of the available modules for use, read the fact sheet here.
The Tower System has a "Primary" and a "Secondary" side. Most of the Tower Modules only send signals through the primary side.
Many of the signals within your chip are not brought out to the tower pins. During the Hardware design process, be careful of this fact.
Most often people plug the USB directly into the module, instead of using the tower USB port.
You can use the Tower System modules without the tower.
Designing your own Tower Module:
Due to the common PCI Express standard pinouts for the tower connector, it is easy to fabricate your own tower module. See the external links section for examples.