RapidIO: The Next Generation Communication Fabric For Embedded Application

Chapter 6. System Level Addressing in RapidIO Systems

The RapidIO architecture assumes that there may be hundreds or thousands of devices in a system. It is not feasible to uniquely identify and separate this many devices on the basis of a single global address space. RapidIO uses device IDs to uniquely identify all of the devices that comprise a RapidIO system.

Because of its focus on bit efficiency, RapidIO defines two models of device addressing. There is a small system model that provides 8 bits of device ID. With 8-bit IDs there could be up to 256 individual devices in a system. The large system model provides for 16-bit device IDs. With 16-bit device IDs, there could be up to 65 536 unique devices in a system. Packets using the small system model are 16 bits smaller than packets using the large system model.

The system level addressing is specified in Part III: Common Transport Specification of the RapidIO specifications. This transport specification is independent of any RapidIO physical or logical layer specification.

This chapter contains the transport layer packet format definitions. Three fields are added to the packet formats to support system level addressing. The transport formats are intended to be fabric independent so that the system interconnect can be anything required for a particular application; therefore all descriptions of the transport fields and their relationship with the logical packets are shown as bit streams.