DP83867CS datasheet(33/114 Pages) TI1

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Valid Data

LOW Quality Data / Link Loss

First Link Failure

Occurrence

Link Drop

Signal

Link Loss

Indication

(Link LED)

DP83867CS, DP83867IS, DP83867E

www.ti.com

SNLS504 – OCTOBER 2015

TDR measurement is allowed in the DP83867 in the following scenarios:

•

While Link partner is disconnected – cable is unplugged at the other side

•

Link partner is connected but remains “quiet” (for example, in power down mode)

•

TDR could be automatically activated when the link fails or is dropped by setting bit 7 of register 0x0009

(CFG1). The results of the TDR run after the link fails will be saved in the TDR registers.

Software could read these registers at any time to apply post processing on the TDR results. This mode is

designed for cases in which the link dropped due to cable disconnections, in which case, after link failure, the line

will be quiet to allow a proper function of the TDR.

9.4.6.2 ALCD

The DP83867 also supports Active Link Cable Diagnostic (ALCD). The ALCD offers a passive method to

estimate the cable length during active link. The ALCD uses passive digital signal processing based on adapted

data, thus enabling measurement of cable length with an active link partner. The ALCD Cable length

measurement accuracy is ±5m for the pair used in the Rx path (due to the passive nature of the test, only the

receive path is measured).

9.4.6.3 Energy Detect

The energy-detector module provides signal-strength indication in various scenarios. Because it is based on an

IIR filter, this robust energy detector has excellent reaction time and reliability. The filter output is compared to

predefined thresholds in order to decide the presence or absence of an incoming signal. The energy detector

also implements hysteresis to avoid jittering in signal-detect indication. In addition it has fully-programmable

thresholds and listening-time periods, enabling shortening of the reaction time if required.

9.4.6.4 Fast Link Drop

The DP83867 includes advanced link-down capabilities that support various real-time applications. The link down

mechanism is configurable and includes enhanced modes that allow extremely fast reaction times to link-drops.

Figure 16. Fast Link Drop Mechanism

As described in Figure 16, the link loss mechanism is based on a time window search period, in which the signal

behavior is monitored. The T1 window is set by default to reduce typical link-drops to less than 1ms in 100M and

0.5ms in 1000M mode.

The DP83867 supports enhanced modes that shorten the window called Fast Link Down mode. In this mode the

T1 window is shortened significantly, in most cases less than 10

μs. In this period of time there are several

criteria allowed to generate link loss event and drop the link:

1. Loss of descrambler sync

2. Receive errors

3. MLT3 errors

4. Mean Squared Error (MSE)

5. Energy loss

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DP83867CS Datasheet(PDF) 33 Page - Texas Instruments

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