LAN9303 参数 Datasheet PDF下载

Small Form Factor Three Port 10/100 Managed Ethernet Switch with Single MII/RMII/Turbo MII

Datasheet

as

specified in the IEEE 802.3 standard. The technology ability bits of these registers are ANDed, and if

there are multiple bits in common, the priority is determined as follows:

100Mbps Full Duplex (highest priority)

100Mbps Half Duplex

10Mbps Full Duplex

10Mbps Half Duplex (lowest priority)

For example, if the full capabilities of the Virtual PHY are advertised (100Mbps, Full Duplex), and if

the link partner is capable of 10Mbps and 100Mbps, then auto-negotiation selects 100Mbps 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. In the event that there are no bits

in common, an emulated

is used.

The

defaults to having all four

ability bits set. These values can be reconfigured via software. Once the auto-negotiation is complete,

any change to the

will not take

affect until the auto-negotiation process is re-run. The emulated link partner default advertised abilities

in the

are dependant on the P0_DUPLEX pin and the

and

configuration straps as described in

of

Neither the Virtual PHY or the emulated link partner support next page capability, remote

faults, or 100BASE-T4.

Note:

The P0_DUPLEX,

and

inputs are considered to be static.

Auto-negotiation is not automatically re-evaluated if these inputs are changed.

If there is at least one common selection between the emulated link partner and the Virtual PHY

advertised abilities, then the auto-negotiation succeeds, the

bit of

the

is set, and the technology

ability bits in the

are set to indicate the emulated link partners abilities.

Note:

For the Virtual PHY, the auto-negotiation register bits (and management of such) are used by

the PMI. So the perception of local and link partner is reversed. The local device is the PMI,

while the link partner is the Switch Fabric. This is consistent with the intention of the Virtual

PHY.

7.3.1.1

Parallel Detection

In the event that there are no common bits between the advertised ability and the emulated link

partners ability, auto-negotiation fails and emulated parallel detect is used. In this case, the

bit of the

will be cleared, and the communication set to half-duplex. The speed is determined

by the

configuration strap. Only one of the technology ability bits in the

will be set,

indicating the emulated parallel detect result.

7.3.1.2

Disabling Auto-Negotiation

Auto-negotiation can be disabled in the Virtual PHY by clearing the

bit

of the

The Virtual PHY will then force its

speed of operation to reflect the speed (Speed

bit) and duplex

bit) of the

The speed and duplex bits in the

should be

ignored when auto-negotiation is enabled.

SMSC LAN9303/LAN9303i

DATASHEET

103

Revision 1.3 (08-27-09)