PCI Express System Architecture

Initial Configuration Accesses

What's Going On During Initialization Time?

During initialization time, the startup configuration software is accessing the configuration registers within each function to determine the presence of a function as well as its resource requirements. Immediately after RST# is removed from a PCI or a PCI-X function, it may not be prepared to service configuration accesses on a timely basis. As an example, a function's configuration registers might not contain valid default values immediately after RST# is removed. Perhaps the function must start backloading this information into its configuration registers from a serial EEPROM. In this case, it could be a substantial amount of time after RST# removal before the function ...