Datasheet
KSZ8081MNX/RNB
DS00002202C-page 26 2016-2018 Microchip Technology Inc.
FIGURE 3-7: TYPICAL CROSSOVER CABLE CONNECTION
3.8 Loopback Mode
The KSZ8081MNX/RNB supports the following loopback operations to verify analog and/or digital data paths.
• Local (digital) loopback
• Remote (analog) loopback
3.8.1 LOCAL (DIGITAL) LOOPBACK
This loopback mode checks the MII/RMII transmit and receive data paths between the KSZ8081MNX/RNB and the
external MAC, and is supported for both speeds (10 Mbps/100 Mbps) at full-duplex.
The loopback data path is shown in Figure 3-8.
1. The MII/RMII MAC transmits frames to the KSZ8081MNX/RNB.
2. Frames are wrapped around inside the KSZ8081MNX/RNB.
3. The KSZ8081MNX/RNB transmits frames back to the MII/RMII MAC.
4. Except the frames back to the RMII MAC, the transmit frames also go out from the copper port.
FIGURE 3-8: LOCAL (DIGITAL) LOOPBACK
RECEIVE PAIR RECEIVE PAIR
TRANSMIT PAIR
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
TRANSMIT PAIR
10/100 ETHERNET
MEDIA DEPENDENT INTERFACE
10/100 ETHERNET
MEDIA DEPENDENT INTERFACE
MODULAR CONNECTOR
(RJ-45)
HUB
(REPEATER OR SWITCH)
CROSSOVER
CABLE
MODULAR CONNECTOR
(RJ-45)
HUB
(REPEATER OR SWITCH)
MII/RMII
MAC
MII/
RMII
AFE
(ANALOG)
KSZ8081MNX/RNB
PCS
(DIGITAL)