Intel PCI-X manual Cable Length Detection copper only, PHY Power Management copper only

PHY Functionality and Features

11.3Cable Length Detection (copper only)

In 100/1000 Mbps operation, the Ethernet controller PHY attempts to indicate the approximate length of the CAT 5 cable attached. The estimated cable length is reported as one of the following ranges:

•<= 50 m

•50 – 80 m

•80 – 110 m

•110 – 140 m

•>= 140 m

The estimated cable length can be obtained by reading the PHY Specific Status Register bits 9:7.

11.4PHY Power Management (copper only)

The Ethernet controller PHY supports power-management based on either link status, MAC power-state, or both. During link-down states, the PHY utilizes its energy-detection capabilities to consume the least amount of power while still being capable of resuming link-up automatically. the Ethernet controller can be configured to automatically reduce PHY power during certain MAC D3 states by re-negotiating a low-speed link (the default behavior, but this can be disabled).

11.4.1Link Down – Energy Detect (copper only)

When the link is operational and the Ethernet controller PHY detects loss of link, it initiates an Auto-Negotiation session. Failing to re-establish link via auto-negotiation, the PHY reverts to an Energy Detect power-down state. Following link loss, the PHY monitors receive energy on the wire. If the PHY detects energy on the wire, it starts to initiate Auto-Negotiation sending FLPs for five seconds. If at the end of five seconds the Auto-Negotiation has not completed, then the PHY stops sending FLPs and returns to monitoring receive energy. While monitoring receive energy, the PHY sends out a single 10 Mbps NLP (Normal Link Pulse) every one second in an attempt to wake up a connected device.

The above behavior is considered to be an advanced Energy-Detect (Energy Detect+) mode of PHY operation. The PHY can also be configured for a regular Energy Detect mode, which behaves similarly, except does not send out NLPs while monitoring receive energy. In this configuration, the Ethernet controller PHY can be woken by a connected device, but does not wake up the connected device itself.

The PHY Specific Control Register bits 9 and 8 described in Section 13.4.7.1.13 are used to configure the specific Energy-Detect mode of behavior for the PHY.

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