Datasheet

DP83640
SNOSAY8E –SEPTEMBER 2007–REVISED APRIL 2013 www.ti.com
• Whether or not a Parallel Detect Fault has occurred
• Whether or not the Link Partner supports the Next Page function
• Whether or not the DP83640 supports the Next Page function
• Whether or not the current page being exchanged by Auto-Negotiation has been received
• Whether or not the Link Partner supports Auto-Negotiation
5.2.3 Auto-Negotiation Parallel Detection
The DP83640 supports the Parallel Detection function as defined in the IEEE 802.3u specification. Parallel
Detection requires both the 10 Mb/s and 100 Mb/s receivers to monitor the receive signal and report link
status to the Auto-Negotiation function. Auto-Negotiation uses this information to configure the correct
technology in the event that the Link Partner does not support Auto-Negotiation but is transmitting link
signals that the 100BASE-TX or 10BASE-T PMAs recognize as valid link signals.
If the DP83640 completes Auto-Negotiation as a result of Parallel Detection, bits 5 and 7 within the
ANLPAR register will be set to reflect the mode of operation 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 negotiation completed via Parallel Detection by reading a zero
in the Link Partner Auto-Negotiation Able bit once the Auto-Negotiation Complete bit is set. If configured
for parallel detect mode and any condition other than a single good link occurs then the parallel detect
fault bit will be set.
5.2.4 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 DP83640 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 DP83640 will resume Auto-
Negotiation after the break_link_timer has expired by issuing FLP (Fast Link Pulse) bursts.
5.2.5 Enabling Auto-Negotiation via Software
It is important to note that if the DP83640 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.
5.2.6 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 Auto-MDIX
When enabled, this function utilizes 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 PHYCR (19h) register, bits [15:14].
42 Configuration Copyright © 2007–2013, Texas Instruments Incorporated
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