Intel GD82559ER manual 2.3 100BASE-TX Transmit Framing, Transmit Driver, Magnetics Modules

Networking Silicon — GD82559ER

Clock

NRZ

1

1

0

0

1

0

0

1

NRZ1 1

1

0

0

1

0

0

1

MLT-31 1 0 0

1 0 0 1

Figure 13. NRZ to MLT-3 Encoding Diagram

6.1.2.3100BASE-TX Transmit Framing

The PHY unit does not differentiate between the fields of the MAC frame containing preamble, Start of Frame Delimiter, data and Cyclic Redundancy Check (CRC). The PHY unit encodes the first byte of the preamble as the “JK” symbol, encodes all other pieces of data according to the 4B/ 5B lookup table, and adds the “TR” code after the end of the packet. The PHY unit scrambles and serializes the data into a 125 Mbps stream, encodes it as MLT-3, and drives it onto the wire.

6.1.2.4Transmit Driver

The transmit differential pair lines are implemented with a digital slope controlled current driver that meets the TP-PMD specifications. Current is sinked from the isolation transformer by the TDP and TDN pins. The conceptual transmit differential waveform for 100 Mbps is illustrated in the following figure.

(V TDP -VTDN )
+1V
0V	t
-1V

Figure 14. Conceptual Transmit Differential Waveform

The magnetics module that is external to the PHY unit converts ITDP and ITDN to the 2.0 Vpp, as required by the TP-PMD specification. The same magnetics used for 100BASE-TX mode should

also work in 10BASE-T mode. The following is a list of current magnetics modules available from several vendors:

Table 4. Magnetics Modules

Vendor	Model/Type	100BASE-TX	10BASE-T
Delta	LF8200A	Yes	Yes
Pulse Engineering	PE-68515	Yes	Yes
Pulse Engineering	H1012	Yes	Yes

Datasheet 39