Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
235
Address Translation Unit (PCI Express)—Intel
®
81341 and 81342
3.0
Address Translation Unit (PCI Express)
This chapter describes the operation modes, setup, and implementation of the module
which interfaces between the PCI Express Link and the Intel
®
81341 and 81342 I/O
Processors (81341 and 81342) internal bus.
3.1
Overview
As indicated in
, the Address Translation Unit (ATU) — the interface between
the PCI Express Link and the on-chip internal bus — consists of the Address Translation
Unit (ATU) and the Expansion ROM Unit.
The ATU supports both inbound and outbound address translation. The ATU provides
access between the PCI Express Link and the 81341 and 81342 internal bus.
Transactions initiated on the PCI Express Link and targeted at the 81341 and 81342
internal bus are referred to as inbound transactions (PCI Express to internal bus).
Transactions initiated on the 81341 and 81342 internal bus and targeted at the PCI
Express Link are referred to as outbound transactions (internal bus to PCI Express).
The ATU accepts multiple inbound or outbound transactions and processes them
simultaneously.
During inbound transactions, the ATU converts PCI addresses (initiated by a PCI
Express Requester) to internal bus addresses and initiates the data transfer on the
81341 and 81342 internal bus. During outbound transactions, the ATU converts
internal bus addresses to PCI addresses and initiates the data transfer on the PCI
Express Link.
The Expansion ROM provides the PCI mechanism for downloading device/board driver
code during system boot sequence. It consists of a separate inbound address range
which accesses a Flash EPROM device connected through the 81341 and 81342
memory controller. Refer to the PCI Local Bus Specification, Revision 2.3 for details of
Expansion ROM usage.
The Address Translation Unit and the Expansion ROM Translation Unit represent a single
function of the multi-function 81341 and 81342 device.
The ATU supports the following PCI Express Lane widths and frequencies delivering up
to 4096 Mbytes/sec of bandwidth:
— Lane Widths: x8, x4, x2, x1
— Link Frequency: 2.5Gbits/s
All PCI Express transactions are protected by link layer CRC.
On the internal interface, the ATU implements the 81341 and 81342 internal bus
protocol which provides for a maximum of 4800 Mbytes/sec of bandwidth.
Address and data are protected by byte-wise parity on the internal bus.