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3.0 Configuration (Continued)

resolved by a random number generation. See IEEE

802.3ab Clause 40.5.1.2 for more details.

Depending on what link the partner is configured to, the

Auto-Negotiation of Master/Slave mode can be resolved to

eight possible outcomes.

(Table 37)

3.3.5 Pause and Asymmetrical Pause Resolution

When Full Duplex operation is selected during priority reso-

lution, the Auto-Negotiation also determines the Flow Con-

trol capabilities of the two link partners. Flow control was

originally introduced to force a busy station’s Link Partner

to stop transmitting data in Full Duplex operation. Unlike

Half Duplex mode of operation where a link partner could

be forced to back off by simply generating collisions, the

Full Duplex operation needed a mechanism to slow down

transmission from a link partner in the event that the receiv-

ing station’s buffers are becoming full. A new MAC control

layer was added to handle the generation and reception of

Pause Frames. Each MAC Controller has to advertise

whether it is capable of processing Pause Frames. In addi-

tion, the MAC Controller advertises if Pause frames can be

handled in both directions, i.e. receive and transmit. If the

MAC Controller only generates Pause frames but does not

respond to Pause frames generated by a link partner, it is

called Asymmetrical Pause.

The advertisement of Pause and Asymmetrical Pause

capabilities is enabled by writing ‘1’ to bits 10 and 11 of

ANAR 0x04. The link partner’s Pause capabilities is stored

ANLPAR 0x05 bits 10 and 11. The MAC Controller has to

read from ANLPAR to determine which Pause mode to

operate. The PHY layer is not involved in Pause resolution

other than simply advertising and reporting of Pause capa-

bilities.

3.3.6 Next Page Support

The DP83865 supports the Auto-Negotiation Next Page

protocol as required by IEEE 802.3u clause 28.2.4.1.7. The

ANNPTR 0x07 allows for the configuration and transmis-

sion of the Next Page. Refer to clause 28 of the IEEE

802.3u standard for detailed information regarding the

Auto-Negotiation Next Page function.

3.3.7 Parallel Detection

The DP83865 supports the Parallel Detection function as

defined in the IEEE 802.3u specification. Parallel Detection

requires the 10/100 Mbps receivers to monitor the receive

signal and report link status to the Auto-Negotiation func-

tion. Auto-Negotiation uses this information to configure

the correct technology in the event that the Link Partner

does not support Auto-Negotiation, yet is transmitting link

signals that the 10BASE-T or 100BASE-X PMA recognize

as valid link signals.

If the DP83865 completes Auto-Negotiation as a result of

Parallel Detection, without Next Page operation, bits 5 and

7 of ANLPAR 0x05 will be set to reflect the mode of opera-

tion present in the Link Partner. Note that bits 4:0 of the

ANLPAR will also be set to 00001 based on a successful

parallel detection to indicate a valid 802.3 selector field.

Software may determine that the negotiation is completed

via Parallel Detection by reading ‘0’ in bit 0 of ANER 0x06

after the Auto-Negotiation Complete bit (bit 5, BMSR 0x01)

is set. If the PHY is configured for parallel detect mode and

any condition other than a good link occurs, the parallel

detect fault bit will set (bit 4, ANER 0x06).

3.3.8 Restart Auto-Negotiation

If a link is established by successful Auto-Negotiation and

then lost, the Auto-Negotiation process will resume to

determine the configuration for the link. This function

ensures that a link can be re-established if the cable

becomes disconnected and re-connected. After Auto-

Negotiation is completed, it may be restarted at any time by

writing ‘1’ to bit 9 of the BMCR 0x00.

A restart Auto-Negotiation request from any entity, such as

a management agent, will cause DP83865 to halt data

transmission or link pulse activity until the break_link_timer

expires (~1500 ms). Consequently, the Link Partner will go

into link fail mode and the resume Auto-Negotiation. The

DP83865

will

resume

Auto-Negotiation

after

the

break_link_timer has expired by transmitting FLP (Fast

Link Pulse) bursts.

3.3.9 Enabling Auto-Negotiation via Software

If the DP83865 is initialized upon power-up with Auto-

Negotiation disabled (forced technology) and the user may

desire to restart Auto-Negotiation, this could be accom-

plished by software access. Bit 12 of BMCR 0x00 should

be cleared and then set for Auto-Negotiation operation to

take place.

3.3.10 Auto-Negotiation Complete Time

Parallel detection and Auto-Negotiation take approximately

2-3 seconds to complete. In addition, Auto-Negotiation with

next page exchange takes approximately 2-3 seconds to

complete, depending on the number of next pages

exchanged.

Refer to Clause 28 of the IEEE 802.3u standard for a full

description of the individual timers related to Auto-Negotia-

tion.

Table 36. 1000BASE-T Single/Multi-Node, AN_EN = 1

MULTI_EN

Forced Mode

Single node, Slave priority mode

Multi-node, Master priority mode

Table 37. Master/Slave Resolution, AN_EN = 1

DP83865

Advertise

Link Partner

Advertise

DP83865

Outcome

Link Partner

Outcome

Mult-node

Manual

Master

Slave

Master

Mult-node

Manual

Slave

Master

Slave

Mult-node

Multi-node

M/S resolved

by random seed

M/S resolved

by random seed

Mult-node

Single-node

Master

Slave

Single-node

Manual

Master

Slave

Master

Single-node

Manual

Slave

Master

Slave

Single-node

Multi-node

Slave

Master

Single-node

M/S resolved

by random seed

M/S resolved

by random seed

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