VSC8541-02 datasheet(21/101 Pages) MICROCHIP

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Functional Descriptions

VMDS-10513 VSC8541-02 Datasheet Revision 4.1

Figure 8 •

Cat5 Media Interface

3.4.2

Cat5 Auto-Negotiation and Parallel Detection

The VSC8541-02 device supports twisted pair auto-negotiation, as defined by IEEE 802.3-2008 Clause

28 and IEEE 802.3az-2010. The auto-negotiation process evaluates the advertised capabilities of the

local PHY and its link partner to determine the best possible operating mode. In particular, auto-

negotiation can determine speed, duplex configuration, and master or slave operating modes for

1000BASE-TX. Auto-negotiation also enables a connected MAC to communicate with its link partner

MAC through the VSC8541-02 device using optional next pages to set attributes that may not otherwise

be defined by the IEEE standard.

If the Category 5 (Cat5) link partner does not support auto-negotiation, the VSC8541-02 device

automatically uses parallel detection to select the appropriate link speed.

Auto-negotiation is disabled by clearing register 0, bit 12. When auto-negotiation is disabled, the state of

Note: While 10BASE-T and 100BASE-TX do not require auto-negotiation, IEEE 802.3-2008 Clause 40 has

defined 1000BASE-T to require auto-negotiation.

3.4.3

Automatic Crossover and Polarity Detection

For trouble-free configuration and management of Ethernet links, the VSC8541-02 device includes a

robust automatic crossover detection feature for all three speeds on the twisted pair interface

(10BASE-T, 100BASE-T, and 1000BASE-T). Known as HP Auto-MDIX, the function is fully compliant

with Clause 40 of IEEE 802.3-2008.

Additionally, the device detects and corrects polarity errors on all MDI pairs—a useful capability that

exceeds the requirements of the standard.

Both HP Auto-MDIX detection and polarity correction are enabled in the device by default. Default

settings can be changed using device register bits 18.5:4. Status bits for each of these functions are

located in register 28.

TXVPA_

TXVNA_

TXVPB_

TXVNB_

TXVPC_

TXVNC_

TXVPD_

TXVND_

PHY Port_n

Transformer

RJ-45

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