PCI Express System Architecture

Each Function Implements a Set of Configuration Registers

Introduction

At the behest of software executing on the processor, the Root Complex initiates configuration transactions to read from or write to a function's configuration registers. These registers are accessed to discover the existence of a function as well as to configure it for normal operation. In addition to memory, IO, and message space, PCI Express also defines a dedicated block of configuration space allocated to each function within which its configuration registers are implemented.

Function Configuration Space

Refer to Figure 19-3 on page 717. Each function's configuration space is 4KB in size and is populated as described in the following two subsections.

Figure 19-3. 4KB ...