Datasheet

 2016 Microchip Technology Inc. DS00002202A-page 27

KSZ8081MNX/RNB

3.8.2 REMOTE (ANALOG) LOOPBACK

This loopback mode checks the line (differential pairs, transformer, RJ-45 connector, Ethernet cable) transmit and

receive data paths between the KSZ8081MNX/RNB and its link partner, and is supported for 100BASE-TX full-duplex

mode only.

The loopback data path is shown in Figure 3-9.

1. The Fast Ethernet (100BASE-TX) PHY link partner transmits frames to the KSZ8081MNX/RNB.

2. Frames are wrapped around inside the KSZ8081MNX/RNB.

3. The KSZ8081MNX/RNB transmits frames back to the Fast Ethernet (100BASE-TX) PHY link partner.

FIGURE 3-9: REMOTE (ANALOG) LOOPBACK

The following programming steps and register settings are used for remote loopback mode.

1.Set Register 0h,

Bits [13] = 1 // Select 100 Mbps speed

Bit [12] = 0 // Disable auto-negotiation

Bit [8] = 1 // Select full-duplex mode

or just auto-negotiate and link up at 100BASE-TX full-duplex mode with the link partner.

2.Set Register 1Fh,

Bit [2] = 1 // Enable remote loopback mode

RJ-45

CAT-5

(UTP)

KSZ8081MNX/RNB

100BASE-TX

LINK PARTNER

AFE

(ANALOG)

PCS

(DIGITAL)

MII/

RMII