2. PCI Interface
47
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
2.3.1
Arbitration Phase: Arbitration for the PCI Bus
PowerSpan II issues a bus request on the PCI bus when it requires access to the PCI bus. When the
PowerSpan II PCI arbiter is active, this request is internal. When it is not enabled the request appears
externally (see
“PCI Interface Arbitration” on page 137
for more information).
The internal PowerSpan II PCI arbiter parks the bus on a PCI master by asserting Px_GNT# to the PCI
master. Bus parking improves the performance of the PowerSpan II PCI Master by reducing arbitration
latency.
2.3.2
Address Phase
The address phase deals with the generation of the PCI address and command encoding.
2.3.2.1
Command Encoding
The encoding on the Px_C/BE# lines indicate the transaction type on the PCI bus. The PCI command
encoding supported by PowerSpan II, and their corresponding transaction types, are shown in