Datasheet

 2007-2016 Microchip Technology Inc. DS00002260A-page 45

LAN8700/LAN8700i

5.4.8.2 Far Loopback

Far loopback is a special test mode for MDI (analog) loopback as indicated by the blue arrows in Figure 5-3. The far

loopback mode is enabled by setting bit register 17 bit 9 to logic one. In this mode, data that is received from the link

partner on the MDI is looped back out to the link partner. The digital interface signals on the local MAC interface are

isolated.

5.4.8.3 Connector Loopback

The LAN8700/LAN8700i maintains reliable transmission over very short cables, and can be tested in a connector loop-

back as shown in Figure 5-4. An RJ45 loopback cable can be used to route the transmit signals an the output of the

transformer back to the receiver inputs, and this loopback will work at both 10 and 100.

FIGURE 5-2: NEAR-END LOOPBACK BLOCK DIAGRAM

Note: This special test mode is only available when operating in RMII mode.

FIGURE 5-3: FAR LOOPBACK BLOCK DIAGRAM

Ethernet Transceiver

10/100

Ethernet

MAC

CAT-5

XFMR

Digital

RXD

TXD

Analog

Far-end system