Small Form Factor Three Port 10/100 Managed Ethernet Switch with Single MII/RMII/Turbo MII
Datasheet
and
bits of the
This allows the PHY to advertise its flow control abilities and auto-negotiate the
flow control settings with its link partner. The default values of these bits are determined via
configuration straps as defined in
The pause flow control settings may also be manually set via the manual flow control registers
and
These registers allow the Switch Fabric ports flow control settings to be manually
set when auto-negotiation is disabled or the respective manual flow control select bit is set (Port
for Port 1,
for Port 2). The currently enabled duplex and flow control settings can
also be monitored via these registers. The flow control values in the
are not affected by the values of the manual flow control
register. Refer to
for additional information.
7.2.5.2
Parallel Detection
If LAN9303/LAN9303i 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 802.3 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
bit in the
is cleared to indicate that the link
partner is not capable of auto-negotiation. If a fault occurs during parallel detection, the
bit of the
is set.
The
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 this register is updated
after completion of parallel detection to reflect the speed capability of the link partner.
7.2.5.3
Restarting Auto-Negotiation
Auto-negotiation can be re-started at any time by setting the
bit of the
Auto-negotiation will also
re-start 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 writing to the
bit of the
the device
will respond by stopping all transmission/receiving operations. Once the internal break link time of
approximately 1200ms has passed in the Auto-negotiation state-machine, the 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.
7.2.5.4
Disabling Auto-Negotiation
Auto-negotiation can be disabled by clearing the
bit of the
The PHY will then force its speed of operation to
reflect the speed (Speed
and duplex (Duplex
of the
The speed
and duplex bits in the
should be
ignored when auto-negotiation is enabled.
7.2.5.5
Half Vs. Full-Duplex
Half-duplex operation relies on the CSMA/CD (Carrier Sense Multiple Access / Collision Detect)
protocol to handle network traffic and collisions. In this mode, the carrier sense signal, CRS, responds
to both transmit and receive activity. If data is received while the PHY is transmitting, a collision results.
Revision 1.3 (08-27-09)
DATASHEET
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SMSC LAN9303/LAN9303i
SMSC [ SMSC CORPORATION ]
