Datasheet

Micrel, Inc.
KSZ8081MNX/KSZ8081RNB
August
19, 2015 28
Revision 1.4
Back-to-Back Mode – 100Mbps Copper Repeater
Two KSZ8081MNX/RNB devices can be connected back-to-back to form a 100Base-TX copper repeater.
Figure 5. KSZ8081MNX/RNB to KSZ8081MNX/RNB Back-to-Back Copper Repeater
MII Back-to-Back Mode (KSZ8081MNX Only)
In MII back-to-back mode, a KSZ8081MNX interfaces with another KSZ8081MNX to provide a complete 100Mbps copper
repeater solution.
The KSZ8081MNX devices are configured to MII back-to-back mode after power-up or reset with the following:
• Strapping pin CONFIG[2:0] (Pins 18, 29, 28) set to 110
• A common 25MHz reference clock connected to XI (Pin 9) of both KSZ8081MNX devices
• MII signals connected as shown in Table 3.
Table 3. MII Signal Connection for MII Back-to-Back Mode (100Base-TX Copper Repeater)
KSZ8081MNX (100Base-TX copper)
[Device 1]
KSZ8081MNX (100Base-TX copper)
[Device 2]
Pin Name
Pin Number
Pin Type
Pin Name
Pin Number
Pin Type
RXDV 18 Output TXEN 23 Input
RXD3 13 Output TXD3 27 Input
RXD2 14 Output TXD2 26 Input
RXD1 15 Output TXD1 25 Input
RXD0 16 Output TXD0 24 Input
TXEN 23 Input RXDV 18 Output
TXD3 27 Input RXD3 13 Output
TXD2 26 Input RXD2 14 Output
TXD1 25 Input RXD1 15 Output
TXD0 24 Input RXD0 16 Output