LXT975 datasheet(30/74 Pages) INTEL

30 / 74 page

LXT974/LXT975 — Fast Ethernet 10/100 Quad Transceivers

Datasheet

2.5

100 Mbps Operation

2.5.1

100BASE-X MII Operations

The LXT974/975 encodes and scrambles the data sent by the MAC, and then transmits it using

MLT3 signaling. The LXT974/975 descrambles and decodes MLT3 data received from the

network.

When the MAC is not actively transmitting data, the LXT974/975 sends out Idle symbols.

The 100BASE-X protocol specifies the use of a 5-bit symbol code on the network media.

However, data is normally transmitted across the MII interface in 4-bit nibbles. The LXT974/975

incorporates a 4B/5B encoder/decoder circuit that translates 4-bit nibbles from the MII into 5-bit

symbols for the 100BASE-X connection, and translates 5-bit symbols from the 100BASE-X

connection into 4-bit nibbles for the MII. Table 12 shows the data conversion flow from nibbles to

symbols. Table 19 on page 32 shows 4B/5B symbol coding (not all symbols are valid).

2.5.2

100BASE-X Network Operations

During 100BASE-X operation, the LXT974/975 transmits and receives 5-bit symbols across the

network link. Figure 14 shows the structure of a standard frame packet. When the MAC is not

actively transmitting data, the LXT974/975 sends out Idle symbols on the line.

In 100TX mode, the LXT974/975 scrambles the data and transmits it to the network using MLT-3

line code. The MLT-3 signals received from the network are descrambled and decoded and sent

across the MII to the MAC.

Figure 12. LXT974/975 Auto-Negotiation Operation

Check Value

0.12

Start

Done

Enable

Auto-Neg/Parallel Detection

Go To Forced

Settings

Attempt Auto-

Negotiation

Listen for 10T

Link Pulses

Listen for 100TX

Idle Symbols

Link Set

YES

Power-Up, Reset,

Link Failure

Disable

Auto-Negotiation

0.12 = 0

0.12 = 1

LXT975 Datasheet(PDF) 30 Page - Intel Corporation

LXT975 Datasheet(HTML) 30 Page - Intel Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74

Datasheet Download

Link URL