Specifications

DP83848Q-Q1

SNLS341C –MARCH 2011–REVISED MARCH 2015

www.ti.com

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 DP83848Q-Q1 supports a configurable Light Emitting Diode (LED) pin link and activity. The PHY

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

See Table 5-2 for LED Mode selection.

Table 5-2. LED Mode Selection

Mode LED_CFG (bit 5) or (pin 33) LED_LINK

ON for Good Link

1 1

OFF for No Link

ON for Good Link

2 0

BLINK for Activity

The LED_LINK pin in Mode 1 indicates the link status of the port. In 100BASE-T mode, link is established

as a result of input receive amplitude compliant with the TP-PMD specifications which will result in internal

generation of signal detect. A 10 Mb/s Link is established as a result of the reception of at least seven

consecutive normal Link Pulses or the reception of a valid 10BASE-T packet. This will cause the assertion

of LED_LINK. LED_LINK will deassert in accordance with the Link Loss Timer as specified in the IEEE

802.3 specification.

The LED_LINK pin in Mode 1 will be OFF when no LINK is present.

The LED_LINK pin in Mode 2 will be ON to indicate Link is good and BLINK to indicate activity is present

on activity.

Because the LED pin is also used as a strap option, the polarity of the LED is dependent on whether the

pin is pulled up or down.

5.3.3.1 LEDs

Because the Auto-Negotiation (AN) strap option shares the LED output pin, the external components

required for strapping and LED usage must be considered in order to avoid contention.

Submit Documentation Feedback

Product Folder Links: DP83848Q-Q1