LXT970ATC datasheet(20/74 Pages) INTEL

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LXT970A — Dual-Speed Fast Ethernet Transceiver

Datasheet

The LXT970A does not support the Signal Detect Function. However, the PMA functions of the

LXT970A guarantee that it will detect invalid link conditions and break down a link, even without

the Signal Detect function.

In applications where the Fiber Interface is not used, the inputs and outputs may be left

unconnected. The Fiber Interface is disabled in power down mode and when the Twisted-Pair

Interface is enabled. When the Fiber Interface is disabled its outputs are pulled to ground.

2.2.3

MII Interface

The LXT970A implements the Media Independent Interface (MII) as defined in the IEEE 802.3.

This interface consists of a data interface and a management interface as shown in Figure 4. The

data interface is used for exchanging data between a 10/100 802.3 compliant Ethernet Media

Access Controller (MAC) and the LXT970A. The management portion of the interface allows

network management functions to control and monitor the LXT970A.

2.2.3.1

Selectable Driver Levels

The LXT970A supports two options for driver-strength capabilities that can be selected via bit

17.3.

High-strength (bit 17.3 = 0, default) MII driver level can effectively source 50 - 60 mA. To avoid

undershoot or overshoot, series termination resistors are recommended on all output signals when

this driver level is selected.

Reduced (bit 17.3 = 1) MII driver level relaxes the pull-down strength of the MII signals by a

factor of ten and the pull-up strength by a factor of eight. Termination resistors are not required on

the MII outputs when this driver level is selected.

Figure 4. MII Interface

LXT970A

Media Access Controller

Media Independent

Interface (MII)

Data

Mgmt

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