KSZ8091RNAIA datasheet(21/62 Pages) MICROCHIP

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 2016 Microchip Technology Inc.

DS00002298A-page 21

KSZ8091RNA/RND

The ‘11’ case, invalid test, occurs when the device is unable to shut down the link partner. In this instance, the test is

not run because it would be impossible for the device to determine if the detected signal is a reflection of the signal

generated or a signal from another source.

Get distance to fault by concatenating Register 1Dh, bits [8:0] and multiplying the result by a constant of 0.38.

The distance to the cable fault can be determined by the following formula:

EQUATION 3-1:

D (distance to cable fault) is expressed in meters.

Concatenated value of Registers 1Dh bits [8:0] should be converted to decimal before multiplying by 0.38.

The constant (0.38) may be calibrated for different cabling conditions, including cables with a velocity of propagation

that varies significantly from the norm.

3.9

NAND Tree Support

The KSZ8091RNA/RND provides parametric NAND tree support for fault detection between chip I/Os and board. The

NAND tree is a chain of nested NAND gates in which each KSZ8091RNA/RND digital I/O (NAND tree input) pin is an

input to one NAND gate along the chain. At the end of the chain, the TXD1 pin provides the output for the nested NAND

gates.

The NAND tree test process includes:

• Enabling NAND tree mode

• Pulling all NAND tree input pins high

• Driving each NAND tree input pin low, sequentially, according to the NAND tree pin order

• Checking the NAND tree output to make sure there is a toggle high-to-low or low-to-high for each NAND tree input

driven low

Table 3-5 list the NAND tree pin order for KSZ8091RNA/RND.

TABLE 3-5:

NAND TREE TEST PIN ORDER FOR KSZ8091RNA/RND

Pin Number

Pin Name

NAND Tree Description

MDIO

Input

MDC

Input

RXD1

Input

RXD0

Input

CRS_DV

Input

REF_CLK

Input

INTRP

Input

TXEN

Input

LED0

Input

TXD0

Input

TXD1

Output

D Distance to cable fault in meters



0.38





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