V62SLASH12615-01XE-R datasheet(35/98 Pages) TI1

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DP83848-EP

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SLLSEC6E – SEPTEMBER 2012 – REVISED JUNE 2019

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Detailed Description

5.3.1.4

Auto-Negotiation Restart

Once Auto-Negotiation has completed, it may be restarted at any time by setting bit 9 (Restart Auto-

Negotiation) of the BMCR to one. If the mode configured by a successful Auto-Negotiation loses a valid

link, then the Auto-Negotiation process will resume and attempt to determine the configuration for the link.

This function ensures that a valid configuration is maintained if the cable becomes disconnected.

A renegotiation request from any entity, such as a management agent, will cause the DP83848-EP to halt

any transmit data and link pulse activity until the break_link_timer expires (~1500 ms). Consequently, the

Link Partner will go into link fail and normal Auto-Negotiation resumes. The DP83848-EP will resume

Auto-Negotiation after the break_link_timer has expired by issuing FLP (Fast Link Pulse) bursts.

5.3.1.5

Enabling Auto-Negotiation via Software

It is important to note that if the DP83848-EP has been initialized upon power-up as a non-auto-

negotiating device (forced technology), and it is then required that Auto-Negotiation or re-Auto-Negotiation

be initiated via software, bit 12 (Auto-Negotiation Enable) of the Basic Mode Control Register (BMCR)

must first be cleared and then set for any Auto-Negotiation function to take effect.

5.3.1.6

Auto-Negotiation Complete Time

Parallel detection and Auto-Negotiation take approximately 2-3 seconds to complete. In addition, Auto-

Negotiation with next page should take approximately 2-3 seconds to complete, depending on the number

of next pages sent.

Refer to Clause 28 of the IEEE 802.3u standard for a full description of the individual timers related to

Auto-Negotiation.

5.3.2

Auto-MDIX

When enabled, this function uses Auto-Negotiation to determine the proper configuration for transmission

and reception of data and subsequently selects the appropriate MDI pair for MDI/MDIX operation. The

function uses a random seed to control switching of the crossover circuitry. This implementation complies

with the corresponding IEEE 802.3 Auto-Negotiation and Crossover Specifications.

Auto-MDIX is enabled by default and can be configured via strap or via PHYCR (19h) register, bits [15:14].

Neither Auto-Negotiation nor Auto-MDIX is required to be enabled in forcing crossover of the MDI pairs.

Forced crossover can be achieved through the FORCE_MDIX bit, bit 14 of PHYCR (19h) register.

Note: Auto-MDIX will not work in a forced mode of operation.

5.3.3

LED Interface

The DP83848-EP supports three configurable light emitting diode (LED) pins. The device supports three

LED configurations: Link, Speed, Activity and Collision. Functions are multiplexed among the LEDs. The

PHYCR for the LEDs can also be selected through address 19h, bits [6:5].

Table 5-2. LED Mode Select

MODE

LED_CGF[1]

(BIT 6)

LED_CFG[0]

(BIT 5)

or (PIN 40)

LED_LINK

LED_SPEED

LED_ACT/COL

don't care

ON for Good Link

OFF for No Link

ON in 100 Mbps

OFF in 10 Mbps

ON for Activity

OFF for No Activity

ON for Good Link

BLINK for Activity

ON in 100 Mbps

OFF in 10 Mbps

ON for Collision

OFF for No Collision

ON for Good Link

BLINK for Activity

ON in 100 Mbps

OFF in 10 Mbps

ON for Full Duplex

OFF for Half Duplex

V62/12615-01XE-R Datasheet(PDF) 35 Page - Texas Instruments

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