±15kV ESD Protected MII/RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support and flexPWR® Technology in a Small Footprint
Datasheet
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.
Note: This special test mode is only available when operating in RMII mode.
Far-end system
TXD
TX
RX
10/100
Ethernet
MAC
X
Link
Partner
CAT-5
XFMR
RXDX
Digital
Analog
SMSC
Ethernet Transceiver
Figure 5.3 Far Loopback Block Diagram
Connector Loopback
5.4.8.3
The LAN8700/LAN8700i maintains reliable transmission over very short cables, and can be tested in
a connector loopback 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.
1
2
TXD
RXD
TX
RX
10/100
Ethernet
MAC
3
4
5
6
7
8
XFMR
Digital
Analog
RJ45 Loopback Cable.
Created by connecting pin 1 to pin 3
and connecting pin 2 to pin 6.
SMSC
Ethernet Transceiver
Figure 5.4 Connector Loopback Block Diagram
SMSC LAN8700/LAN8700i
Revision 2.3 (04-12-11)
DATA5S5HEET
SMSC [ SMSC CORPORATION ]
