Cable Diagnostics The LinkMD <" />
參數(shù)資料
型號: KSZ8041FTL-S
廠商: Micrel Inc
文件頁數(shù): 28/65頁
文件大?。?/td> 0K
描述: IC TXRX PHY 10/100 SGL 48TQFP
標(biāo)準(zhǔn)包裝: 250
系列: *
Micrel, Inc.
KSZ8041TL/FTL/MLL
December 2009
34
M9999-120909-1.2
LinkMD
Cable Diagnostics
The LinkMD
feature utilizes time domain reflectometry (TDR) to analyze the cabling plant for common cabling problems,
such as open circuits, short circuits and impedance mismatches.
LinkMD
works by sending a pulse of known amplitude and duration down the MDI and MDI-X pairs, and then analyzing
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
is initiated by accessing register 1Dh, the LinkMD Control/Status Register, in conjunction with register 1Fh, the
PHY Control 2 Register.
Usage
The following test procedure demonstrates how to use LinkMD
for cable diagnostic:
1.
Disable auto MDI/MDI-X by writing a ‘1’ to register 1Fh bit 13 to enable manual control over the differential pair
used to transmit the LinkMD
pulse.
2.
Select the differential pair to transmit the LinkMD
pulse with register 1Fh bit 14.
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:
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)
The ‘11’ case, invalid test, occurs if the KSZ8041TL/FTL/MLL 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/MLL to determine if the detected
signal is a reflection of the signal generated by the KSZ8041TL/FTL/MLL, or a signal from its link partner.
6.
Get distance to fault by multiplying the decimal value in register 1Dh bits [8:0] by a constant of 0.4. The distance,
D (expressed in meters), to the cable fault is determined by the following formula:
D (distance to cable fault) = 0.4 x {decimal value of register 1Dh bits [8:0]}
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.
Power Management
The KSZ8041TL/FTL/MLL 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. Under power saving mode, the KSZ8041TL/FTL/MLL
shuts down all transceiver blocks, except for transmitter, 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/MLL 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/MLL disables all internal
functions, except for the MII management interface.
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