GD82559C S L3DF Intel, GD82559C S L3DF Datasheet - Page 47

• Manufacturer Part Number: GD82559C S L3DF
• Manufacturer: Intel

Specifications of GD82559C S L3DF

• Lead Free Status / Rohs Status: Not Compliant

5.0
5.1
5.1.1
5.1.2
5.1.2.1
Datasheet
82559 Physical Layer Functional Description
100BASE-TX PHY Unit
100BASE-TX Transmit Clock Generation
A 25 MHz crystal or a 25 MHz oscillator is used to drive the PHY unit’s X1 and X2 pins. The PHY
unit derives its internal transmit digital clocks from this crystal or oscillator input. The internal
Transmit Clock signal is a derivative of the 25 MHz internal clock. The accuracy of the external
crystal or oscillator must be ± 0.005% (50 ppm).
100BASE-TX Transmit Blocks
The transmit subsection of the PHY unit accepts nibble-wide data from the CSMA/CD unit. The
transmit subsection passes data unconditionally to the 4B/5B encoder.
The 4B/5B encoder accepts nibble-wide data (4 bits) from the CSMA unit and compiles it into 5-
bit-wide parallel symbols. These symbols are scrambled and serialized into a 125 Mbps bit stream,
converted by the analog transmit driver into a MLT-3 waveform format, and transmitted onto the
Unshielded Twisted Pair (UTP) or Shielded Twisted Pair (STP) wire.
100BASE-TX 4B/5B Encoder
The 4B/5B encoder complies with the IEEE 802.3u 100BASE-TX standard. Four bits are encoded
according to the transmit 4B/5B lookup table. The lookup table matches a 5-bit code to each 4-bit
code.
The table below illustrates the 4B/5B encoding scheme associated with the given symbol.
Table 2.
4B/5B Encoder
Symbol
A
B
C
0
1
2
3
4
5
6
7
8
9
5B Symbol Code
01001
10100
10101
01010
10010
01011
10011
10110
11010
11110
01110
01111
10111
4B Nibble Code
0000
0001
0010
0011
0100
0101
0110
1000
1001
1010
1011
1100
0111
Networking Silicon — 82559
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