FALXT972MCCA4 datasheet(24/92 Pages) INTEL

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Intel

® LXT972M Single-Port 10/100 Mbps PHY Transceiver

Datasheet

Document Number: 302875-005

Revision Date: 27-Oct-2005

5.2.1.1

Twisted-Pair Interface

The LXT972M Transceiver supports either 100BASE-TX or 10BASE-T connections over 100

Ω,

Category

5, Unshielded Twisted Pair (UTP) cable. When operating at 100 Mbps, the LXT972M

Transceiver continuously transmits and receives MLT3 symbols. When not transmitting data, the

LXT972M Transceiver generates “IDLE” symbols.

During 10 Mbps operation, Manchester-encoded data is exchanged. When no data is being

exchanged, the line is left in an idle state. Link pulses are transmitted periodically to keep the link

up.

Only a transformer, RJ-45 connector, load resistor, and bypass capacitors are required to complete

this interface. On the transmit side, the LXT972M Transceiver has an active internal termination

and does not require external termination resistors. Intel's patented waveshaping technology shapes

the outgoing signal to help reduce the need for external EMI filters. Four slew rate settings allow

the designer to match the output waveform to the magnetic characteristics. On the receive side, the

internal impedance is high enough that it has no practical effect on the external termination circuit.

(For the slew rate settings, see Table 56, “Transmit Control Register - Address 30, Hex 1E” on

page 89.)

Note:

On the LXT972M Transceiver, MDIX crossover (MDIX) is supported by board design.

5.2.1.2

Remote Fault Detection and Reporting

The LXT972M Transceiver supports the remote fault detection and reporting mechanisms.

“Remote Fault” refers to a MAC-to-MAC communication function that is transparent to PHY layer

devices. It is used only during auto-negotiation, and is applicable only to twisted-pair links.

Remote Fault Detection. Register bit 4.13 in the Auto-Negotiation Advertisement Register is

reserved for Remote Fault indications. It is typically used when re-starting the auto-negotiation

sequence to indicate to the link partner that the link is down because the advertising device

detected a local fault.

When the LXT972M Transceiver receives a Remote Fault indication from its partner during auto-

negotiation, the following occurs:

• Register bit 5.13 in the Link Partner Base Page Ability Register is set.

• Remote Fault Register bit 1.4 in the MII Status Register is set to pass this information to the

local controller.

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