ksz8041tl-ftl Micrel Semiconductor, ksz8041tl-ftl Datasheet - Page 29

• Manufacturer Part Number: ksz8041tl-ftl
• Description: 10base-t/100base-tx/100base-fx Physical Layer Transceiver
• Manufacturer: Micrel Semiconductor

Micrel, Inc.
LinkMD
The LinkMD
such as open circuits, short circuits and impedance mismatches.
LinkMD
the shape of the reflected signal. Timing the pulse duration gives an indication of the distance to the cabling fault with
maximum distance of 200m and accuracy of +/-2m. Internal circuitry computes the TDR information and presents it in a
user-readable digital format.
Note: Cable diagnostics are only valid for copper connections and do not support fiber optic operation.
Access
LinkMD
PHY Control 2 Register.
Usage
The following test procedure demonstrates how to use LinkMD
Power Management
The KSZ8041TL/FTL offers the following power management modes:
Power Saving Mode
This mode is used to reduce power consumption when the cable is unplugged. It is in effect when auto-negotiation mode
is enabled, cable is disconnected, and register 1Fh bit 10 is set to 1 (default setting). Under power saving mode, the
KSZ8041TL/FTL shuts down all transceiver blocks, except for energy detect and PLL circuits. Additionally, in MII mode,
the RXC clock output is disabled. RXC clock is enabled after the cable is connected and link is established.
Power saving mode is disabled by writing a zero to register 1Fh bit 10.
Power Down Mode
This mode is used to power down the entire KSZ8041TL/FTL device when it is not in use. Power down mode is enabled
by writing a one to register 0h bit 11. In the power down state, the KSZ8041TL/FTL disables all internal functions, except
for the MII management interface.
April 2007
1. Disable auto MDI/MDI-X by writing a ‘1’ to register 1Fh bit 13 to enable manual control over the differential pair
2. Select the differential pair to transmit the LinkMD
3. Start cable diagnostic test by writing a ‘1’ to register 1Dh bit 15. This enable bit is self-clearing.
4. Wait (poll) for register 1Dh bit 15 to return a ‘0’, indicating cable diagnostic test is completed.
5. Read cable diagnostic test results in register 1Dh bits [14:13]. The results are as follows:
6. Get distance to fault by multiplying the decimal value in register 1Dh bits [8:0] by a constant of 0.4. The distance,
The 0.4 constant can be calibrated for different cable types and cabling conditions, such as cables with velocity of
propagation that varies significantly from the norm.
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used to transmit the LinkMD
The ‘11’ case, invalid test, occurs if the KSZ8041TL/FTL is unable to shut down the link partner. In this instance,
the test is not run, since it would be impossible for the KSZ8041TL/FTL to determine if the detected signal is a
reflection of the signal generated by the KSZ8041TL/FTL, or a signal from its link partner.
D (expressed in meters), to the cable fault is determined by the following formula:
works by sending a pulse of known amplitude and duration down the MDI and MDI-X pairs, and then analyzing
is initiated by accessing register 1Dh, the LinkMD
Cable Diagnostics
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feature utilizes time domain reflectometry (TDR) to analyze the cabling plant for common cabling problems,
00 = normal condition (valid test)
01 = open condition detected in cable (valid test)
10 = short condition detected in cable (valid test)
11 = cable diagnostic test failed (invalid test)
D (distance to cable fault) = 0.4 x {decimal value of register 1Dh bits [8:0]}
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pulse.
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pulse with register 1Fh bit 14.
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Control/Status Register, in conjunction with register 1Fh, the
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for cable diagnostic:
M9999-042707-1.1
KSZ8041TL/FTL