LXT9763 — Fast Ethernet 10/100 Hex Transceiver with Full MII
Preamble Handling
When the MAC asserts TX_EN, the PCS substitutes a /J/K symbol pair, also known as the Start of
Stream Delimiter (SSD), for the first two nibbles received across the MII. The PCS layer continues
to encode the remaining MII data, following Table 9 on page 30, until TX_EN is de-asserted. It
then returns to supplying IDLE symbols to the line driver.
In the receive direction, the PCS layer performs the opposite function, substituting two preamble
nibbles for the SSD.
Dribble Bits
The LXT9763 handles dribbles bits in all modes. If between 1-4 dribble bits are received, the
nibble is passed across the MII, padded with 1s if necessary. If between 5-7 dribble bits are
received, the second nibble is not sent onto the MII bus
Figure 15. Protocol Sublayers
MII Interface
LXT9763
PCS
Sublayer
Encoder/Decoder
Serializer/De-serializer
PMA
Link/Carrier Detect
Sublayer
PECL Interface
PMD
Sublayer
Scrambler/
De-scrambler
Fiber Transceiver
100BASE-TX
100BASE-FX
.
Table 9. 4B/5B Coding
4B Code
3 2 1 0
5B Code
4 3 2 1 0
Code Type
Name
Interpretation
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0
1
2
3
1 1 1 1 0
0 1 0 0 1
1 0 1 0 0
1 0 1 0 1
Data 0
Data 1
Data 2
Data 3
1. The /I/ (Idle) code group is sent continuously between frames.
2. The /J/ and /K/ (SSD) code groups are always sent in pairs; /K/ follows /J/.
3. The /T/ and /R/ (ESD) code groups are always sent in pairs; /R/ follows /T/.
4. An /H/ (Error) code group is used to signal an error condition.
30
Datasheet
INTEL [ INTEL ]
