KSZ8893-MQL Micrel Semiconductor, Inc., KSZ8893-MQL Datasheet - Page 47

• Manufacturer Part Number: KSZ8893-MQL
• Description: Integrated 3-Port 10/100 Managed Switch with PHYs
• Manufacturer: Micrel Semiconductor, Inc.

Loopback Support
The KSZ8893MQL provides loopback support for remote diagnostic of failure. In loopback mode, the speed at
both PHY ports needs to be set to 100BASE-TX. Two types of loopback are supported: Far-end Loopback and
Near-end (Remote) Loopback.
Far-end Loopback
Far-end loopback is conducted between the KSZ8893MQL’s two PHY ports. The loopback path starts at the
“Originating.” PHY port’s receive inputs (RXP/RXM), wraps around at the “loopback” PHY port’s PMD/PMA, and
ends at the “Originating” PHY port’s transmit outputs (TXP/TXM).
Bit [0] of registers 29 and 45 is used to enable far-end loopback for ports 1 and 2, respectively. Alternatively, the
MII Management register 0, bit [14] can be used to enable far-end loopback.
The far-end loopback path is illustrated in the following figure.
Micrel
November 2005
R X P /
R X M
Figure 12: Far-End Loopback Path
P M D /P M A
P M D /P M A
S w itc h
O riginating
P H Y P o rt
L oo p B ack
P H Y P o rt
M A C
M A C
P C S
P C S
47
T X P /
T X M
KSZ8893MQL/MQLI
M9999-111705