LAN9252SLASHML datasheet(139/329 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS00001909A-page 139

LAN9252

11.2.12.2

Matched Cable Diagnostics

Matched cable diagnostics enable cable length estimation on 100 Mbps-linked cables of up to 120 meters. If there is an

active 100 Mb link, the approximate distance to the link partner can be estimated using the PHY x Cable Length Register

(PHY_CABLE_LEN_x). If the cable is properly terminated, but there is no active 100 Mb link (the link partner is disabled,

nonfunctional, the link is at 10 Mb, etc.), the cable length cannot be estimated and the PHY x Cable Length Register

(PHY_CABLE_LEN_x) should be ignored. The estimated distance to the link partner can be determined via the Cable

Length (CBLN) field of the PHY x Cable Length Register (PHY_CABLE_LEN_x) using the lookup table provided in

Table 11-8. The typical cable length measurement margin of error for a matched cable case is +/- 20 m. The matched

cable length margin of error is consistent for all cable types from 0 to 120 m.

TABLE 11-7:

TYPICAL MEASUREMENT ERROR FOR SHORTED CABLE (+/- METERS)

PHYSICAL DISTANCE

TO FAULT

SELECTED PROPAGATION CONSTANT

PSHORT =

Unknown

PSHORT =

CAT 6

PSHORT =

CAT 5E

PSHORT =

CAT 5

CAT 6 Cable, 0-100 m

CAT 5E Cable, 0-100 m

CAT 5 Cable, 0-100 m

CAT 6 Cable, 101-160 m

CAT 5E Cable, 101-160 m

CAT 5 Cable, 101-160 m

TABLE 11-8:

MATCH CASE ESTIMATED CABLE LENGTH (CBLN) LOOKUP

CBLN Field Value

Estimated Cable Length

0 - 3

517

627

738

849

959

102

113

123

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