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Copper PHY Link Configuration — Intel
®
82575EB Gigabit Ethernet Controller
324632-003 Intel
®
82575EB Gigabit Ethernet Controller
Revision: 2.1 Software Developer’s Manual and EEPROM Guide
January 2011 249
9.3.2 Copper PHY Link Configuration
When operating with the internal PHY, link configuration is generally determined by PHY Auto-
Negotiation. The software device driver must intervene in cases where a successful link is not
negotiated or the programmer desires to manually configure the link. The following sections discuss the
methods of link configuration for copper PHY operation.
9.3.2.1 PHY Auto-Negotiation (Speed, Duplex, and Flow
Control)
When using a copper PHY, the PHY performs the Auto-Negotiation function. The actual operational
details of this operation are described in the IEEE P802.3ab draft standard and are not included here.
Auto-Negotiation provides a method for two link partners to exchange information in a systematic
manner in order to establish a link configuration providing the highest common level of functionality
supported by both partners. Once configured, the link partners exchange configuration information to
resolve link settings such as:
• Speed: 10/100/1000 Mb/s
• Duplex: Full- or Half-
• Flow Control Operation
PHY specific information required for establishing the link is also exchanged.
Note: If flow control is enabled in the 82575, the settings for the desired flow control behavior
must be set by software in the PHY registers and Auto-Negotiation restarted. After Auto-
Negotiation completes, the software device driver must read the PHY registers to determine
the resolved flow control behavior of the link and reflect these in the MAC register settings
(CTRL.TFCE and CTRL.RFCE).
Once PHY Auto-negotiation completes, the PHY asserts a link indication (LINK) to the MAC.
Software must have set the Set Link Up bit in the Device Control Register (CTRL.SLU)
before the MAC recognizes the LINK indication from the PHY and can consider the link to be
up.
9.3.2.2 MAC Speed Resolution
For proper link operation, both the MAC and PHY must be configured for the same speed of link
operation. The speed of the link can be determined and set by several methods with the 82575. These
include:
• Software-forced configuration of the MAC speed setting based on PHY indications and can be
determined as follows:
— Software reads of PHY registers directly to determine the PHY’s auto-negotiated speed
— Software reads the PHY’s internal PHY-to-MAC speed indication (SPD_IND) using the MAC
STATUS.SPEED register
— Software signals the MAC to attempt to auto-detect the PHY speed from the PHY-to-MAC
RX_CLK, then programs the MAC speed accordingly
• MAC automatically detects and sets the link speed of the MAC based on PHY indications by using
the PHY's internal PHY-to-MAC speed indication (SPD_IND) and automatically setting the MAC
speed.
9.3.2.2.1 Forcing MAC Speed