VSC7440 datasheet(53/444 Pages) MICROSEMI

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Functional Descriptions

VMDS-10492 VSC7440 Datasheet Revision 4.2

Important The EPG is intended for use with laboratory or in-system testing equipment only. Do not use

the EPG testing feature when the PHY is connected to a live network.

To use the EPG feature, set PHY_1000BT_EPG2.EPG_ENA to 1.

When PHY_1000BT_EPG2.EPG_RUN_ENA is set to 1, the PHY begins transmitting Ethernet packets

based on the settings in the PHY_1000BT_EPG1 and PHY_1000BT_EPG2 registers. These registers

set:

•

Source and destination addresses for each packet

•

Packet size

•

Inter-packet gap

•

FCS state

•

Transmit duration

•

Payload pattern

If PHY_1000BT_EPG1.TRANSMIT_DURATION_CFG is set to 0, PHY_1000BT_EPG1.EPG_RUN_ENA

is cleared automatically after 30,000,000 packets are transmitted.

3.8.7.2

CRC Counters

Two separate CRC counters are available in the PHY: a 14-bit good CRC counter available through

PHY_CRC_GOOD_CNT.CRC_GOOD_PKT_CNT and a separate 8-bit bad CRC counter in

PHY_CTRL_EXT4.CRC_1000BT_CNT.

3.8.7.3

Far-End Loopback

The far-end loopback testing feature is enabled by setting

PHY_CTRL_EXT1.FAR_END_LOOPBACK_ENA to 1. When enabled, it forces incoming data from a link

partner on the current media interface, into the MAC interface of the PHY, to be re-transmitted back to the

link partner on the media interface as shown in the following illustration. The incoming data also appears

on the receive data pins of the MAC interface. Data present on the transmit data pins of the MAC

interface is ignored when using this testing feature.

Figure 15 •

Far-End Loopback Diagram

3.8.7.4

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 Diagram

Link Partner

PHY

Switch

Cat5

Link Partner

PHY

Switch

Cat5

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