2. PCI Interface
46
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
2.3
PCI Master Interface
In order for PowerSpan II to be a PCI master in a transaction the Bus Master (BM) bit, in the
Control and Status Register.” on page 251
, must be set. With this bit set, PowerSpan II is PCI Master in
a transaction in the following instances:
•
Servicing a request by:
— the processor bus: PowerSpan II is accessed as a PB slave
— the alternate PCI Interface: PowerSpan II is accessed as a PCI target
•
processing a transfer by one of the four PowerSpan II DMA channels
•
generating a configuration or IACK cycle because of a PowerSpan II register access
This section discusses only the first three conditions listed above. Configuration and IACK cycles are
discussed in
“Configuration and IACK Cycle Generation” on page 246
The operation of the PCI Master is described by dividing the PCI master transaction into the following
phases:
•
Arbitration phase: This section
describes how PowerSpan II requests the PCI bus and its response
to bus parking.
•
Address phase: This section discusses the generation of the PCI address and command encoding.
•
Data phase: This section describes control of burst length.
•
Terminations: This section
explains the terminations supported by
PowerSpan II, how they are mapped to the source port (Processor Interface or the alternate PCI
Interface), and exception handling.
PowerSpan II cannot be both master and target on a PCI bus at the same time.