VSC8601 Datasheet
Functional Descriptions
Figure 12.
Far-End Loopback
Link Partner
SimpliPHY
MAC
RX
TX
RXD
TXD
Cat5
3.13.4
Near-End Loopback
When the near-end loopback testing feature is enabled (by setting the device register
bit 0.14 to 1), data on the transmit data pins (TXD) is looped back onto the device
received data pins (RXD) as illustrated in the following illustration. When using this
testing feature, no data is transmitted over the network.
Figure 13.
Near-End Loopback
Link Partner
SimpliPHY
MAC
RX
TX
RXD
TXD
Cat5
3.13.5
Connector Loopback
The connector loopback testing feature allows for the twisted pair interface to be looped
back externally. When using this feature, the PHY must be connected to a loopback
connector or a loopback cable. Pair A should be connected to pair B and pair C to
pair D, as shown in the following illustration. The connector loopback feature functions
at all available interface speeds.
Figure 14.
Connector Loopback
A
RXD
B
Cat5
SimpliPHY
MAC
C
D
TXD
When using the connector loopback testing feature, the device auto-negotiation, speed,
and duplex configuration is set using device registers 0, 4, and 9. For 1000BASE-T
Revision 4.1
September 2009
Page 32
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
