Example Read From a PCI Express Device
The Read Receives the Deferred Response
Figure 52-3. Read Transaction Receives a Deferred Response
In this example, one of the processors initiates either an IO read or a memory-mapped IO read from a register within the IEEE 1394 FireWire controller on the PCI bus. The Root Complex acts as the Response Agent for the transaction and, because it will take awhile to obtain the requested read data, it issues a Deferred response to the read transaction:
The read transaction request is issued in BCLK cycle ...