KSZ8841_11 Datasheet, PDF (42/105 Pages) Micrel Semiconductor – Single-Port Ethernet MAC Controller with Non-PCI Interface

Micrel, Inc.
KSZ8841-16/32 MQL/MVL/MBL
Loopback Support
The KSZ8841M provides Near-end (Remote) loopback support for remote diagnostic of failure. In loopback mode, the
speed at the PHY port will be set to 100BASE-TX full-duplex mode.
Near-end (Remote) Loopback
Near-end (Remote) loopback is conducted at PHY port 1of the KSZ8841M. The loopback path starts at the PHY port’s
receive inputs (RXP1/RXM1), wraps around at the same PHY port’s PMD/PMA, and ends at the PHY port’s transmit
outputs (TXP1/TXM1).
Bit [1] of register P1PHYCTRL is used to enable near-end loopback for port 1. Alternatively, Bit [9] of register P1SCSLMD
can also be used to enable near-end loopback. The ports 1 near-end loopback path is illustrated in the following Figure
12.
RXP1 /
RXM1
PHY Port 1
Near-end (remote)
Loopback
TXP1 /
TXM1
PMD1/PMA1
PCS1
MAC1
RXQ/TXQ
QMU/DMA
Bus I/F Unit
Figure 12. PHY Port 1 Near-end (Remote) Loopback Path
October 2007
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M9999-102207-1.6