TLK111_14 Datasheet, PDF (20/110 Pages) Texas Instruments – PHYTER® Industrial Temperature 10/100Mbs Ethernet Physical Layer Transceiver

TLK111
SLLSEF8B – AUGUST 2013 – REVISED JANUARY 2014
www.ti.com
3.13 Cable Diagnostics
With the vast deployment of Ethernet devices, the need for reliable, comprehensive and user-friendly
cable diagnostic tool is more important than ever. The wide variety of cables, topologies, and connectors
deployed results in the need to non-intrusively identify and report cable faults. The TI cable-diagnostic unit
provides extensive information about cable integrity.
The TLK111 offers the following capabilities in its Cable Diagnostic tools kit:
1. Time Domain Reflectometry (TDR)
2. Active Link Cable Diagnostic (ALCD)
3.13.1 TDR
The TLK111 uses Time Domain Reflectometry (TDR) to determine the quality of the cables, connectors,
and terminations in addition to estimating the cable length. Some of the possible problems that can be
diagnosed include opens, shorts, cable impedance mismatch, bad connectors, termination mismatches,
cross faults, cross shorts and any other discontinuities along the cable.
The TLK111 transmits a test pulse of known amplitude (1V or 2.5V) down each of the two pairs of an
attached cable. The transmitted signal continues down the cable and reflects from each cable
imperfection, fault, bad connector, and from the end of the cable itself. After the pulse transmission the
TLK111 measures the return time and amplitude of all these reflected pulses. This technique enables
measuring the distance and magnitude (impedance) of non-terminated cables (open or short),
discontinuities (bad connectors), and improperly-terminated cables with ±1m accuracy.
The TLK111 also uses data averaging to reduce noise and improve accuracy. The TLK111 can record up
to five reflections within the tested pair. If more than 5 reflections are recorded, the TLK111 saves the first
5 of them. If a cross fault is detected, the TDR saves the first location of the cross fault and up to 4
reflections in the tested channel. The TLK111 TDR can measure cables up to 200m in length.
For all TDR measurements, the transformation between time of arrival and physical distance is done by
the external host using minor computations (such as multiplication, addition and lookup tables). The host
must know the expected propagation delay of the cable, which depends, among other things, on the cable
category (for example, CAT5, CAT5e, or CAT6).
TDR measurement is allowed in the TLK111 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 8 of register
0x0009 (SWSCR1). The results of the TDR run after the link fails will be saved in the TDR registers.
The SW 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 after link failure,
the line will be quiet to allow a proper function of the TDR.
3.13.2 ALCD
The TLK111 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).
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