RapidIO: The Next Generation Communication Fabric For Embedded Application

4.1. INTRODUCTION

This chapter describes the set of input and output (I/O) logical operations and their associated transactions as defined in Part I of the RapidIO specification. I/O logical operations provide support for basic reads and writes to and from memory spaces located within a RapidIO system. Details of the transaction types, packet formats, and other necessary transaction information are presented.

The I/O operations are achieved through the use of request/response transaction pairs. The transaction pairs operate through a RapidIO fabric. The RapidIO fabric does not track the transactions as they travel through the fabric and, from the perspective of the fabric, there is no explicit or implicit relationship between request transactions and the responses to those requests. Although there may be intermediate switch devices within a system and hence multiple packet transmissions, from the perspective of the RapidIO logical layer there will be a single request transaction and a single response transaction if required. Intermediate switch devices do not differentiate between request and response transactions. Their role is simply to forward a transaction towards its final destination.

There are six basic I/O operations defined in the RapidIO architecture. Table 4.1 presents the defined operations, the transactions that are used to perform the operation and a description of the operation.