LXT975B datasheet(31/74 Pages) INTEL

31 / 74 page

Fast Ethernet 10/100 Quad Transceivers — LXT974/LXT975

Datasheet

In 100FX mode, the LXT974/975 transmits and receives NRZI signals across the PECL interface.

An external 100FX transceiver module is required to complete the fiber connection.

As shown in Figure 14, the MAC starts each transmission with a preamble pattern. As soon as the

LXT974/975 detects the start of preamble, it transmits a J/K symbol (Start of Stream Delimiter,

SSD) to the network. It then encodes and transmits the rest of the packet, including the balance of

the preamble, the Start of Frame Delimiter (SFD), packet data, and CRC. Once the packet ends,

the LXT974/975 transmits the T/R symbol End-of-Stream Delimiter (ESD) and then returns to

transmitting Idle symbols.

Figure 13. 100BASE-TX Data Flow

Figure 14. 100BASE-TX Frame Structure

1. Four independent MII ports serve four independent Network ports. Network port configurations are independently

selectable. MII port speed is set to match the associated Network port.

2. The Scrambler can be bypassed by setting 19.3 = 1.

Parallel

Serial

Parallel

4B/5B

5B/4B

MLT3

-1

Transition = 1.

No Transition = 0.

All transitions must follow

pattern: 0, +1, 0, -1, 0, +1...

Scramble

De-

Scramble

Standard MII Mode Data Flow

SFD

64-Bit Preamble

(8 Octets)

Start of Frame

Delimiter (SFD)

Destination and Source

Address (6 Octets each)

Packet Length

(2 Octets)

Data Field

(Pad to minimum packet size)

Frame Check Field

(4 Octets)

CRC

InterFrame Gap / Idle Code

(> 12 Octets)

Replaced by

/T/R/ code-groups

End of Stream Delimiter (ESD)

IFG

Replaced by

/J/K/ code-groups

Start of Stream

Delimiter (SSD)

LXT975B Datasheet(PDF) 31 Page - Intel Corporation

LXT975B Datasheet(HTML) 31 Page - Intel Corporation

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