Small Footprint MII/RMII 10/100 Ethernet Transceiver for Automotive Applications
Datasheet
If the full capabilities of the transceiver are advertised (100M, Full Duplex), and if the link partner is
capable of 10M and 100M, then auto-negotiation selects 100M as the highest performance mode. If
the link partner is capable of half and full duplex modes, then auto-negotiation selects full duplex as
the highest performance operation.
Once a capability match has been determined, the link code words are repeated with the acknowledge
bit set. Any difference in the main content of the link code words at this time will cause auto-negotiation
to re-start. Auto-negotiation will also re-start if not all of the required FLP bursts are received.
The capabilities advertised during auto-negotiation by the transceiver are initially determined by the
logic levels latched on the MODE[2:0] configuration straps after reset completes. These configuration
straps can also be used to disable auto-negotiation on power-up. Refer to Section 3.7.2, "MODE[2:0]:
Mode Configuration," on page 38 for additional information.
Writing the bits 8 through 5 of the Auto Negotiation Advertisement Register allows software control of
the capabilities advertised by the transceiver. Writing the Auto Negotiation Advertisement Register
does not automatically re-start auto-negotiation. The Restart Auto-Negotiate bit of the Basic Control
Register must be set before the new abilities will be advertised. Auto-negotiation can also be disabled
via software by clearing the Auto-Negotiation Enable bit of the Basic Control Register.
Note: The device does not support “Next Page” capability.
3.2.1
Parallel Detection
If the LAN88710AM/LAN88710BM is connected to a device lacking the ability to auto-negotiate (i.e.
no FLPs are detected), it is able to determine the speed of the link based on either 100M MLT-3
symbols or 10M Normal Link Pulses. In this case the link is presumed to be half duplex per the IEEE
standard. This ability is known as “Parallel Detection.” This feature ensures interoperability with legacy
link partners. If a link is formed via parallel detection, then the Link Partner Auto-Negotiation Able bit
of the Auto Negotiation Expansion Register is cleared to indicate that the Link Partner is not capable
of auto-negotiation. The controller has access to this information via the management interface. If a
fault occurs during parallel detection, the Parallel Detection Fault bit of Link Partner Auto-Negotiation
Able is set.
Auto Negotiation Link Partner Ability Register is used to store the link partner ability information, which
is coded in the received FLPs. If the link partner is not auto-negotiation capable, then the Auto
Negotiation Link Partner Ability Register is updated after completion of parallel detection to reflect the
speed capability of the link partner.
3.2.2
Restarting Auto-Negotiation
Auto-negotiation can be restarted at any time by setting the Restart Auto-Negotiate bit of the Basic
Control Register. Auto-negotiation will also restart if the link is broken at any time. A broken link is
caused by signal loss. This may occur because of a cable break, or because of an interruption in the
signal transmitted by the link partner. Auto-negotiation resumes in an attempt to determine the new
link configuration.
If the management entity re-starts auto-negotiation by setting the Restart Auto-Negotiate bit of the
Basic Control Register, the LAN88710AM/LAN88710BM will respond by stopping all
transmission/receiving operations. Once the break_link_timer is completed in the auto-negotiation
state-machine (approximately 1200 ms), auto-negotiation will re-start. In this case, the link partner will
have also dropped the link due to lack of a received signal, so it too will resume auto-negotiation.
SMSC LAN88710AM/LAN88710BM
29
Revision 1.1 (05-26-10)
DATASHEET
SMSC [ SMSC CORPORATION ]
