VSC8504-02 datasheet(26/131 Pages) MICROSEMI

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Functional Descriptions

VMDS-10507 VSC8504-02 Datasheet Revision 4.2

3.5.1

Voltage Mode Line Driver

Unlike many other gigabit PHYs, the VSC8504-02 uses a patented voltage mode line driver that allows it

to fully integrate the series termination resistors, which are required to connect the PHY’s Cat5 interface

to an external 1:1 transformer. Also, the interface does not require the user to place an external voltage

on the center tap of the magnetic. The following illustration shows the connections.

Figure 17 •

Cat5 Media Interface

3.5.2

Cat5 Autonegotiation and Parallel Detection

The VSC8504-02 supports twisted pair autonegotiation, as defined by IEEE 802.3-2008 Clause 28 and

IEEE 802.3az-2010. The autonegotiation process evaluates the advertised capabilities of the local PHY

and its link partner to determine the best possible operating mode. In particular, autonegotiation can

determine speed, duplex configuration, and master or slave operating modes for 1000BASE-TX.

Autonegotiation also enables a connected MAC to communicate with its link partner MAC through the

VSC8504-02 using optional next pages, which set attributes that may not otherwise be defined by the

IEEE standard.

If the Category 5 (Cat5) link partner does not support autonegotiation, the VSC8504-02 automatically

uses parallel detection to select the appropriate link speed.

Autonegotiation is disabled by clearing register 0, bit 12. When autonegotiation is disabled, the state of

Note: While 10BASE-T and 100BASE-TX do not require autonegotiation, Clause 40 has defined 1000BASE-T

to require autonegotiation.

3.5.3

Automatic Crossover and Polarity Detection

For trouble-free configuration and management of Ethernet links, the VSC8504-02 includes a robust

automatic crossover detection feature for all three speeds on the twisted pair interface (10BASE-T,

TXVPA_

TXVNA_

TXVPB_

TXVNB_

TXVPC_

TXVNC_

TXVPD_

TXVND_

PHY Port_n

Transformer

A+

A–

B+

B–

C+

C–

D+

D–

RJ-45

Ω

1000 pF,

2 kV

0.1µF

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