ksz8851-mql Micrel Semiconductor, ksz8851-mql Datasheet - Page 41

• Manufacturer Part Number: ksz8851-mql
• Description: Single-port Ethernet Mac Controller With 8/16-bit Or 32-bit Non-pci Interface
• Manufacturer: Micrel Semiconductor

Micrel, Inc.
KSZ8851-16/32 MQL/MQLI
Loopback Support
The KSZ8851M provides two loopback modes, one is Near-end (Remote) loopback to support for remote diagnostic of
failure at line side, and the other is Far-end (Local) loopback to support for local diagnostic of failure at host side. 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 1 of the KSZ8851M. 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 [9] of register P1SCLMD (0xF4) is used to enable near-end loopback. The ports 1 near-end loopback path is illustrated
in the following Figure 11.
Far-end (Local) Loopback
Far-end (Local) loopback is conducted at Host of the KSZ8851M. The loopback path starts at the host port’s transmit
inputs (Tx data), wraps around at the PHY port’s PMD/PMA, and ends at the host port’s receive outputs (Rx data)
Bit [14] of register P1MBCR (0xE4) is used to enable far-end loopback at host side. The host far-end loopback path is
illustrated in the following Figure 11.
Figure 11. PHY Port 1 Near-end (Remote) and Host Far-end (Local) Loopback Paths
February 2009
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