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DJLXT908LC

Universal 3.3V 10BASE-T and AUI Transceiver

Intel 

Universal 3.3V 10BASE-T and AUI Transceiver — LXT908

Table 1. LXT908 Signal Descriptions (Continued)

Pin#

PLCC LQFP

Symbol

40

3

PAUI

41

4

DIP

42

5

DIN

43

7

DOP

44

8

DON

I/O

Description

Port/AUI Select. In Manual Port Select mode (AUTOSEL Low),

I

PAUI selects the active port. When PAUI is High, the AUI port is

selected. When PAUI is Low, the TP port is selected. In Auto Port

Select mode, PAUI must be tied to ground.

I AUI Receive Pair. Differential input pair from the AUI transceiver DI

I circuit. The input is Manchester encoded.

O AUI Transmit Pair. A differential output driver pair for the AUI

O transceiver cable. The output is Manchester encoded.

2.0

Functional Description

2.1

2.1.1

Introduction

The LXT908 Universal 10BASE-T and AUI Transceiver performs the physical layer signaling

(PLS) and Media Attachment Unit (MAU) functions as defined by the IEEE 802.3 specification. It

functions as an AUI (PLS-Only device) for use with 10BASE-2 or 10BASE-5 coaxial cable

networks, or as an Integrated PLS/MAU for use with 10BASE-T twisted-pair (TP) networks. In

addition to standard 10 Mbps operation, the LXT908 also supports full-duplex 20 Mbps operation.

The LXT908 interfaces a back-end controller to either an AUI drop cable or a twisted-pair cable.

The controller interface includes transmit and receive clock and NRZ data channels, as well as

mode control logic and signaling. The AUI interface comprises three circuits: Data Output (DO),

Data Input (DI), and Collision (CI). The twisted-pair interface comprises two circuits: Twisted-Pair

Input (TPI) and Twisted-Pair Output (TPO). In addition to the three basic interfaces, the LXT908

contains an internal crystal oscillator and four LED drivers for visual status reporting.

Functions are defined from the back end controller side of the interface. The LXT908 Transmit

function refers to data transmitted by the back end to the AUI cable (PLS-Only mode) or to the

twisted-pair network (Integrated PLS/MAU mode). The LXT908 Receive function refers to data

received by the back end from the AUI cable (PLS-Only) or from the twisted-pair network

(Integrated PLS/MAU mode). In the integrated PLS/MAU mode, the LXT908 performs all

required MAU functions defined by the IEEE 802.3 10BASE–T specification, such as collision

detection, link integrity testing, signal quality error messaging, jabber control, and loopback. In the

PLS-Only mode, the LXT908 receives incoming signals from the AUI DI circuit with

±18 ns of jitter and drives the AUI DO circuit.

Controller Compatibility Modes

The LXT908 is compatible with most industry-standard controllers including devices produced by

Advanced Micro Devices (AMD), Motorola, Intel, Fujitsu, National Semiconductor, Seeq, and

Texas Instruments, as well as custom controllers. Five different control signal timing and polarity

schemes (Modes 1 through 5) are required to achieve this compatibility. Mode select pins (MD2:0)

determine Controller compatibility modes as listed in Table 2 on page 12. Refer to Test

Specifications for a complete set of timing diagrams for each mode.

Datasheet

11

Document #: 249049

Revision #: 002

Rev. Date: June 19, 2001

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