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Functional Descriptions

VMDS-10488 VSC7511 Datasheet Revision 4.2

Figure 15 •

Far-End Loopback

3.5.7.4

Near-End Loopback

When the near-end loopback testing feature is enabled (by setting PHY_CTRL.LOOPBACK_ENA to 1),

data on the transmit data pins (TXD) is looped back in the PCS block, onto the device receive data pins

(RXD), as shown in the following illustration. When using this testing feature, no data is transmitted over

the network.

Figure 16 •

Near-End Loopback

3.5.7.5

Connector Loopback

The connector loopback testing feature allows the twisted pair interface to be looped back externally.

When using the connector loopback feature, the PHY must be connected to a loopback connector or a

loopback cable. Pair A must be connected to pair B, and pair C to pair D, as shown in the following

illustration. The connector loopback feature functions at all available interface speeds.

Figure 17 •

Connector Loopback

When using the connector loopback testing feature, the device auto-negotiation, speed, and duplex

configuration is set using device registers 0, 4, and 9. For 1000BASE-T connector loopback, the

following additional writes are required, executed in the following steps:

Enable the 1000BASE-T connector loopback. Set

PHY_CTRL_EXT2.CON_LOOPBACK_1000BT_ENA to 1.

Disable pair swap correction. Set PHY_CTRL_EXT2.CON_LOOPBACK_1000BT_ENA to 1.

3.5.8

VeriPHY™ Cable Diagnostics

The integrated transceivers include a comprehensive suite of cable diagnostic functions that are

available through the on-board processor. These functions enable cable operating conditions and

status to be accessed and checked. The VeriPHY suite has the ability to identify the cable

length and operating conditions and to isolate common faults that can occur on the Cat5 twisted pair

cabling.

For the functional details of the VeriPHY suite and the operating instructions, see the ENT-AN0125,

PHY, Integrated PHY-Switch VeriPHY - Cable Diagnostics Feature Application Note.

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