KS8001L View Datasheet(PDF) - Micrel
Part Name
Description
MFG CO.
'KS8001L' PDF : 46 Pages View PDF
Micrel
KSZ8001
Vcc
Rx +/-
Tx +/-
FTx
FRx
To the SD pin of the
Fiber Module
21 22
Pin
KSZ8001
RxD
TxD
TxC/
Ref_CLK
TxC/
Ref_CLK
KSZ8001
(Fiber Mode)
Pin
Pin
34
21 22
TxD
RxD
Vcc
OSC
50 MHz
LinkMD Cable Diagnostics
The KSZ8001 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 MDIX pairs and analyzing the shape of the reflected signal. Timing the duration gives an indication of the distance to the
cabling fault with maximum distance of 200 m and accuracy of +/- 2 m. Cable diagnostics are only valid for copper connections and
do not support fiber optic operation.
LinkMD is used by accessing register 1dh, the LinkMD Control/Status register in conjunction with register 1fh, the 100BASE-TX PHY
Controller register. To use LinkMD, HP Auto-MDIX is disabled by writing a ‘1’ to 1f:13 to enable manual control over which pair is
used to transmit the LinkMD pulse. The self-clearing Cable diagnostic test enable bit, 1d.15 is set to ‘1’ to start the test on this pair.
When 1d.15 returns to ‘0’, the test is complete. The test result is returned in 1d.14:13 and the distance is returned in 1d.8:0. The
cable diagnostic test results are as follows:
• 00 = Valid test, normal condition
• 01 = Valid test, open circuit in cable
• 10 = Valid test, short circuit in cable
• 11 = Invalid test, LinkMD failed
The ‘11’ case, Invalid test, occurs when it is not possible for the KSZ8001 to shut down the link partner. In this case, the test is not
run, since it would not be possible for the KSZ8001 to determine if the detected signal is a reflection of the signal generated or a
signal from another source.
Cable length can be determined by multiplying the contents of 1d.8:0 by 0.39. This constant may be calibrated for different cabling
conditions, including cables with a velocity of propagation that varies significantly from the norm.
June 2009
Revision 1.04
23
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