LAN9252SLASHML datasheet(136/329 Pages) MICROCHIP

136 / 329 page

LAN9252

DS00001909A-page 136

 2015 Microchip Technology Inc.

11.2.10.3

PHY Power-Down Reset

After the PHY has returned from a power-down state, a reset of the PHY is automatically generated. The PHY power-

down modes do not reload or reset the PHY registers. Refer to Section 11.2.8, "PHY Power-Down Modes," on page 131

for additional information.

11.2.11

LINK INTEGRITY TEST

The device performs the link integrity test as outlined in the IEEE 802.3u (clause 24-15) Link Monitor state diagram. The

link status is multiplexed with the 10 Mbps link status to form the Link Status bit in the PHY x Basic Status Register

(PHY_BASIC_STATUS_x) and to drive the LINK LED functions.

The DSP indicates a valid MLT-3 waveform present on the RXPx and RXNx signals as defined by the ANSI X3.263 TP-

PMD standard, to the Link Monitor state-machine, using the internal DATA_VALID signal. When DATA_VALID is

asserted, the control logic moves into a Link-Ready state and waits for an enable from the auto-negotiation block. When

received, the Link-Up state is entered, and the Transmit and Receive logic blocks become active. Should auto-negoti-

ation be disabled, the link integrity logic moves immediately to the Link-Up state when the DATA_VALID is asserted.

To allow the line to stabilize, the link integrity logic will wait a minimum of 330 ms from the time DATA_VALID is asserted

until the Link-Ready state is entered. Should the DATA_VALID input be negated at any time, this logic will immediately

negate the Link signal and enter the Link-Down state.

11.2.12

CABLE DIAGNOSTICS

The PHYs provide cable diagnostics which allow for open/short and length detection of the Ethernet cable. The cable

diagnostics consist of two primary modes of operation:

• Time Domain Reflectometry (TDR) Cable Diagnostics

TDR cable diagnostics enable the detection of open or shorted cabling on the TX or RX pair, as well as cable

length estimation to the open/short fault.

• Matched Cable Diagnostics

Matched cable diagnostics enable cable length estimation on 100 Mbps-linked cables.

Refer to the following sub-sections for details on proper operation of each cable diagnostics mode.

11.2.12.1

Time Domain Reflectometry (TDR) Cable Diagnostics

The PHYs provide TDR cable diagnostics which enable the detection of open or shorted cabling on the TX or RX pair,

as well as cable length estimation to the open/short fault. To utilize the TDR cable diagnostics, Auto-MDIX and Auto

Negotiation must be disabled, and the PHY must be forced to 100 Mbps full-duplex mode. These actions must be per-

formed before setting the TDR Enable bit in the PHY x TDR Control/Status Register (PHY_TDR_CONTROL_STAT_x).

With Auto-MDIX disabled, the TDR will test the TX or RX pair selected by register bit 27.13 (Auto-MDIX State (AMDIX-

STATE)). Proper cable testing should include a test of each pair. TDR cable diagnostics is not appropriate for 100BASE-

FX mode. When TDR testing is complete, prior register settings may be restored. Figure 11-5 provides a flow diagram

of proper TDR usage.

Note:

Cable diagnostics are not used for 100BASE-FX mode.

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