VSC7511 datasheet(52/324 Pages) MICROSEMI

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Functional Descriptions

VMDS-10488 VSC7511 Datasheet Revision 4.2

3.5.2.2

Cat5 Auto-Negotiation and Parallel Detection

The integrated transceivers support twisted pair auto-negotiation as defined by clause 28 of the IEEE

802.3-2008. 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 allows the device to communicate with the link partner (through the optional “next pages”) to set

attributes that may not otherwise be defined by the IEEE standard.

If the Cat5 link partner does not support auto-negotiation, the device automatically use parallel detection

to select the appropriate link speed.

Auto-negotiation can be disabled by clearing PHY_CTRL.AUTONEG_ENA. If auto-negotiation is

disabled, the state of the SPEED_SEL_MSB_CFG, SPEED_SEL_LSB_CFG, and

DUPLEX_MODE_CFG fields in the PHY_CTRL register determine the device’s operating speed and

duplex mode. Note that while 10BASE-T and 100BASE-T do not require auto-negotiation, 1000BASE-T

does require it (defined by clause 40).

3.5.2.3

1000BASE-T Forced Mode Support

The integrated transceivers provides support for a 1000BASE-T forced test mode. In this mode, the PHY

can be forced into 1000BASE-T mode and does not require manual setting of master/slave at the two

ends of the link. This mode is only for test purposes. Do not use in normal operation. To configure a PHY

in this mode, set PHY_EEE_CTRL.FORCE_1000BT_ENA = 1, with

PHY_CTRL.SPEED_SEL_LSB_CFG = 1 and PHY_CTRL.SPEED_SEL_LSB_CFG = 0.

3.5.2.4

Automatic Crossover and Polarity Detection

For trouble-free configuration and management of Ethernet links, the integrated transceivers include 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 the IEEE 802.3-2002.

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 the POL_INV_DIS and PAIR_SWAP_DIS fields in the

PHY_BYPASS_CTRL register. Status bits for each of these functions are located in the

PHY_AUX_CTRL_STAT register.

The integrated transceivers can be configured to perform HP Auto-MDIX, even when auto-negotiation is

disabled (PHY_CTRL.AUTONEG_ENA = 0) and the link is forced into 10/100 speeds. To enable the HP

Auto-MDIX feature, set PHY_BYPASS_CTRL.FORCED_SPEED_AUTO_MDIX_DIS to 0.

The HP Auto-MDIX algorithm successfully detects, corrects, and operates with any of the MDI wiring pair

combinations listed in the following table.

3.5.2.5

Manual MDI/MDI-X Setting

As an alternative to HP Auto-MDIX detection, the PHY can be forced to be MDI or MDI X using

PHY_EXT_MODE_CTRL.FORCE_MDI_CROSSOVER_ENA. Setting this field to 10 forces MDI, and

setting 11 forces MDI-X. Leaving the bits 00 enables the MDI/MDI-X setting to be based on

FORCED_SPEED_AUTO_MDIX_DIS and PAIR_SWAP_DIS in the register PHY_BYPASS_CTRL.

Table 21 •

Supported MDI Pair Combinations

1, 2

3, 6

4, 5

7, 8

Mode

Normal MDI

Normal MDI-X

Normal MDI with pair swap on C and D pair

Normal MDI-X with pair swap on C and D pair

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