KSZ8873MLLJ datasheet(41/108 Pages) MICREL | Integrated 3-Port 10/100 Managed Switch with PHYs

41 / 108 page

Micrel, Inc.

KSZ8873MLLJ

September 2011

M9999-091911-1.8

Loopback Support

The KSZ8873MLLJ 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 KSZ8873MLLJ’s two PHY ports. The loopback is limited to few package a

time for diagnosis purpose and can not support large traffic. 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.

Figure 14. Far-End Loopback Path

KSZ8873MLLJ Datasheet(PDF) 41 Page - Micrel Semiconductor