DP83848J_14 Datasheet, PDF (17/81 Pages) Texas Instruments – PHYTER Mini LS Commercial Temperature Single Port 10/100 Mb/s Ethernet Transceiver

2.1.3 Auto-Negotiation Parallel Detection
The DP83848J supports the Parallel Detection function as
defined in the IEEE 802.3u specification. Parallel Detec-
tion 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-Negoti-
ation but is transmitting link signals that the 100BASE-TX
or 10BASE-T PMAs recognize as valid link signals.
If the DP83848J completes Auto-Negotiation as a result of
Parallel Detection, bit 5 or bit 7 within the ANLPAR regis-
ter 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 Detec-
tion 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.
Auto-MDIX is enabled by default and can be configured
via strap or via PHYCR (0x19h) 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 (0x19h) register.
Note: Auto-MDIX will not work in a forced mode of opera-
tion.
2.1.4 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-Negotia-
tion 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 discon-
nected.
A renegotiation request from any entity, such as a man-
agement agent, will cause the DP83848J 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-Negotia-
tion resumes. The DP83848J will resume Auto-Negotia-
tion after the break_link_timer has expired by issuing FLP
(Fast Link Pulse) bursts.
2.1.5 Auto-Negotiation Complete Time
Parallel detection and Auto-Negotiation take approxi-
mately 2-3 seconds to complete. In addition, Auto-Negoti-
ation 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-Negoti-
ation.
2.2 AUTO-MDIX
When enabled, this function utilizes Auto-Negotiation to
determine the proper configuration for transmission and
reception of data and subsequently selects the appropri-
ate MDI pair for MDI/MDIX operation. The function uses a
random seed to control switching of the crossover cir-
cuitry. This implementation complies with the correspond-
ing IEEE 802.3 Auto-Negotiation and Crossover
Specifications.
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