KSZ8851SNL-BBE-EVAL Micrel Inc, KSZ8851SNL-BBE-EVAL Datasheet - Page 32

• Manufacturer Part Number: KSZ8851SNL-BBE-EVAL
• Description: BOARD EVAL MAC/PHY FOR KSZ8851
• Manufacturer: Micrel Inc
• Series: LinkMD®r

Specifications of KSZ8851SNL-BBE-EVAL

• Design Resources: BeagleBoard Zippy2
• Main Purpose: Interface, Ethernet Controller (PHY and MAC)
• Embedded: No
• Utilized Ic / Part: KSZ8851SNL
• Primary Attributes: 1 Port, 100BASE-TX/10BASE-T
• Secondary Attributes: SPI Interface, LinkMD Cable Diagnostics
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-3602; KSZ8851SNL-BBE-EVL; ZIPPY2

Micrel, Inc.
KSZ8851SNL/SNLI
Loopback Support
The KSZ8851SNL 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 KSZ8851SNL. The loopback path starts at the PHY port’s
receive inputs (RXP/RXM), wraps around at the same PHY port’s PMD/PMA, and ends at the PHY port’s transmit outputs
(TXP/TXM).
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 14.
Far-end (Local) Loopback
Far-end (Local) loopback is conducted at Host of the KSZ8851SNL. The loopback path starts at the host SPI FIFO write
to transmit data, wraps around at the PHY port’s PMD/PMA, and ends at the host SPI FIFO read to receive 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 14.
Figure 14. PHY Port 1 Near-end (Remote) and Host Far-end (Local) Loopback Paths
August 2009
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M9999-083109-2.0