Backplane bus protocols determine—electrically and mechanically—how signals are dropped off or picked up at every device attached to the line. Protocols determine how cards pass information, the speed of data transfer, the maximum number and type of peripheral devices allowed, and the physical size and layout of the system. In general, the choice of the correct protocol for a backplane design is a complex decision that involves many design compromises. No one solution will give the best performance in each design category.

This section discusses the readily available Peripheral Component Interconnect (PCI)-based and VERSAmodule Eurocard (VME)-based backplane protocols. The goal of this section is to provide an understanding of what is necessary to implement a backplane protocol and how to choose the protocol that best fits the design needs.