Datasheet

LAN8740A/LAN8740Ai
DS00001987A-page 52  2013-2015 Microchip Technology Inc.
3.8.12.3 Connector Loopback
The device maintains reliable transmission over very short cables and can be tested in a connector loopback as shown
in Figure 3-16. An RJ45 loopback cable can be used to route the transmit signals from the output of the transformer
back to the receiver inputs. The loopback works at both 10 and 100 Mbps.
FIGURE 3-16: CONNECTOR LOOPBACK BLOCK DIAGRAM
Microchip
Ethernet Transceiver
10/100
Ethernet
MAC
XFMR
Digital
RXD
TXD
Analog
RX
TX
1
2
3
4
5
6
7
8
RJ45 Loopback Cable.
Created by connecting pin 1 to pin 3
and connecting pin 2 to pin 6.