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Dual Port Characteristics — Intel
®
82575EB Gigabit Ethernet Controller
324632-003 Intel
®
82575EB Gigabit Ethernet Controller
Revision: 2.1 Software Developer’s Manual and EEPROM Guide
January 2011 279
13.0 Dual Port Characteristics
The 82575 architecture includes two instances both the MAC and PHY. With both MAC/PHY pairs
operating, the 82575 appears as a multi-function PCIe* device containing two identically-functioning
devices. To avoid confusion, each MAC (when combined with either an internal/external PHY or SerDes)
is referred to as “LANx”, where x = “A” or
x = “B” to refer to each logical LAN device (LAN 0 or LAN 1).
This section details specific features common to each MAC or PHY, resources/interfaces for which
dedicated independent hardware/software interfaces exists for each LAN, as well as resources which
are shared by both LAN devices.
The 82575 normally appears to the system as a single, multi-function PCIe* device. It provides the
ability to selectively disable one of the internal LAN functions, thereby allowing it to appear to the
system as a single-function, single-LAN device. The mechanisms for controlling this behavior and the
resulting appearance to the system are described in Section 13.5 entitled, “LAN Disable”.
13.1 Features of Each MAC
The 82575 is designed to have the capability to appear as two independent instances of a gigabit
controller. The following section details major features that can be considered to be distinct features
available to each 82575 MAC independently.
13.1.1 PCIe* Interface
The 82575 contains a single physical PCIe* core interface. The 82575 is designed so that each of the
logical LAN devices (LAN 0, LAN 1) appears as a distinct function implementing, amongst other
registers, the following PCIe* device header space:
Byte Offset Byte 0 Byte 1 Byte 2 Byte 3
0h Device ID Vendor ID
4h Status Register Command Register
8h Class Code 020000h Revision ID (02h)
Ch 00h Header Type 00h Latency Timer Cache Line Size
10h Base Address 0
14h Base Address 1
18h Base Address 2
1Ch Base Address 3
20h Base Address 4
24h Base Address 5