1. Functional Overview
26
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
1.2.3
PCI Host Bridge
PowerSpan II is designed for host bridge applications. The PowerPC processor generates configuration
cycles on the PCI bus in the same way as that found in conventional PCI host bridges. In addition, with
concurrent reads and low device latency, the PCI Target Interface on PowerSpan II is specifically
designed to allow low latency access to host packet memory for I/O controllers on either of the PCI
buses.
1.2.4
PCI Bus Arbitration
Each PCI Interface has an integrated PCI bus arbiter. Each arbiter supports four external bus requesters.
An additional three bus requesters can be assigned between the two PCI arbiters.
The PCI arbiters implement a fairness algorithm, two round robin priority levels and flexible bus
parking options.
1.3
Processor Bus Interface
The PowerSpan II provides a direct-connect 64-bit interface to the PowerQUICC II (MPC8260),
MPC7xx, PowerPC
TM
7xx, and the Wintegra WinPath
TM
processors. The direct-connect support for
these interfaces has been extensively verified during product development with processor functional
models as well as with a hardware emulation methodology. This verification ensures any potential
interface issues are identified and resolved by IDT before PowerSpan II customers begin to design their
own systems.
PowerSpan II supports processor (60x) bus extended cycles on the Processor Interface. Extended cycle
support means more flexible bursting and more efficient use of the processor bandwidth.
1.3.1
Address Decoding
Instead of consuming chip selects from the processor, PowerSpan II performs its own address decoding
for up to eight memory (slave) images to the PCI bus from the processor bus. This allows a flexible
mapping of processor transactions to PCI cycle types.
1.3.2
Processor Bus Arbitration
The Processor Interface has an integrated bus arbiter. The Processor Interface supports three external
bus masters for applications involving multiple processors. The processor bus arbiter implements two
levels of priority, where devices programmed into a specific priority level operate in a round robin
fashion in that level.
1.4
DMA Controller
PowerSpan II provides four independent, bidirectional DMA channels. Each DMA channel is capable
of Linked-List or Direct mode transfers.
Each DMA channel transfers data from any-port to any-port. For example, from PCI-1 to PCI-2,
Processor Bus to PCI-1, or Processor Bus and Processor Bus. High throughput data transfer is coupled
by flexible endian mapping and a range of status bits mappable to external interrupts.