Datasheet

DP83620

www.ti.com

SNLS339C –JANUARY 2011–REVISED APRIL 2013

5 Configuration

This section includes information on the various configuration options available with the DP83620. The

configuration options described below include:

— Media Configuration

— Auto-Negotiation

— PHY Address and LEDs

— Half Duplex vs. Full Duplex

— Isolate mode

— Loopback mode

— BIST

5.1 MEDIA CONFIGURATION

The DP83620 supports both Twister Pair (100BASE-TX and 10BASE-T) and Fiber (100BASE-FX) media.

The port may be configured for Twisted Pair (TP) or Fiber (FX) operation by strap option or by register

access.

At power-up/reset, the state of the RX_ER pin will select the media for the port. The default selection is

twisted pair mode, while an external pull-down will select FX mode of operation. Strapping the port into FX

mode also automatically sets the Far-End Fault Enable, bit 3 of PCSR (16h), the Scramble Bypass, bit 1

of PCSR (16h) and the Descrambler Bypass, bit 0 of PCSR (16h). In addition, the media selection may be

controlled by writing to bit 6, FX_EN, of PCSR (16h).

5.2 AUTO-NEGOTIATION

The Auto-Negotiation function provides a mechanism for exchanging configuration information between

two ends of a link segment and automatically selecting the highest performance mode of operation

supported by both devices. Fast Link Pulse (FLP) Bursts provide the signalling used to communicate

Auto-Negotiation abilities between two devices at each end of a link segment. For further detail regarding

Auto-Negotiation, refer to Clause 28 of the IEEE 802.3u specification. The DP83620 supports four

different Ethernet protocols (10 Mb/s Half Duplex, 10 Mb/s Full Duplex, 100 Mb/s Half Duplex, and 100

Mb/s Full Duplex), so the inclusion of Auto-Negotiation ensures that the highest performance protocol will

be selected based on the advertised ability of the Link Partner. The Auto-Negotiation function within the

DP83620 can be controlled either by internal register access or by the use of the AN_EN, AN1 and AN0

pins.

5.2.1 Auto-Negotiation Pin Control

The state of AN_EN, AN0 and AN1 determines whether the DP83620 is forced into a specific mode or

Auto-Negotiation will advertise a specific ability (or set of abilities) as given in Table 5-1. These pins allow

configuration options to be selected without requiring internal register access.

The state of AN_EN, AN0 and AN1, upon power-up/reset, determines the state of bits [8:5] of the ANAR

The Auto-Negotiation function selected at power-up or reset can be changed at any time by writing to the

Basic Mode Control Register (BMCR) at address 00h.

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