FALXT972MCCA4 datasheet(46/92 Pages) INTEL

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Intel

® LXT972M Single-Port 10/100 Mbps PHY Transceiver

Datasheet

Document Number: 302875-005

Revision Date: 27-Oct-2005

5.7.3.1

Physical Coding Sublayer

The Physical Coding Sublayer (PCS) provides the MII interface, as well as the 4B/5B encoding/

decoding function.

For 100BASE-TX operation, the PCS layer provides IDLE symbols to the PMD-layer line driver

as long as TX_EN is de-asserted.

5.7.3.1.1

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 the 4B/5B coding in Table 15, 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. In 100 Mbps operation, preamble is always passed through the PCS layer to

the MII interface.

Table 15. 4B/5B Coding (Sheet 1 of 2)

Code Type

4B Code

3 2 1 0

Name

5B Code

4 3 2 1 0

Interpretation

DATA

0 0 0 0

1 1 1 1 0

Data 0

0 0 0 1

0 1 0 0 1

Data 1

0 0 1 0

1 0 1 0 0

Data 2

0 0 1 1

1 0 1 0 1

Data 3

0 1 0 0

0 1 0 1 0

Data 4

0 1 0 1

0 1 0 1 1

Data 5

0 1 1 0

0 1 1 1 0

Data 6

0 1 1 1

0 1 1 1 1

Data 7

1 0 0 0

1 0 0 1 0

Data 8

1 0 0 1

1 0 0 1 1

Data 9

1 0 1 0

1 0 1 1 0

Data A

1 0 1 1

1 0 1 1 1

Data B

1 1 0 0

1 1 0 1 0

Data C

1 1 0 1

1 1 0 1 1

Data D

1 1 1 0

1 1 1 0 0

Data E

1 1 1 1

1 1 1 0 1

Data F

IDLE

undefined

I 1

1 1 1 11

Used as inter-stream fill code

1. The /I/ (Idle) code group is sent continuously between frames.

2. The /J/ and /K/ (SSD) code groups are always sent in pairs, and /K/ follows /J/.

3. The /T/ and /R/ (ESD) code groups are always sent in pairs, and /R/ follows /T/.

4. An /H/ (Error) code group is used to signal an error condition.

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