TLK110 Datasheet, PDF (37/104 Pages) Texas Instruments – Industrial Temp, Single Port 10/100Mbs Ethernet Physical Layer

TLK110
www.ti.com
SLLS901A – DECEMBER 2011 – REVISED FEBRUARY 2012
5.6 Link Down Functionality
The TLK110 includes advanced link-down capabilities that support various real-time applications. The link-
down mechanism of the TLK110 is configurable and includes enhanced modes that allow extremely fast
reaction times to link-drops.
Valid Data
First Link Failure
Occurrence
LOW Quality Data / Link Loss
Signal
Link Loss
Indication
(Link LED)
Link Drop
T1
Figure 5-3. TLK110 Link Loss Mechanism
As described in Figure 5-3, the TLK110 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.
The TLK110 supports enhanced modes that shorten the window called Fast Link Down mode. In this
mode, which can be configured in Software Strap Control Register 3 (SWSCR3), address 0x000B, bits
3:0, the T1 window is shortened significantly, in most cases less than 10µs. In this period of time there are
several criteria allowed to generate link loss event and drop the link:
1. Count RX Error in the MII interface: When a predefined number of 32 RX Error occurrences in time
window of 10µs is reached the link will drop.
2. Count MLT3 Errors at the signal processing output (100BT uses MLT3 coding, and when a violation of
this coding is detected, an MLT3 error is declared). When a predefined number of 20 errors
occurrences in 10µs is reached the link will drop.
3. Count Low Signal Quality Threshold crossing (When the signal quality is under a certain threshold that
allows proper link conditions). When a predefined number of 20 occurrences in 10µs is reached, the
link will drop.
4. Signal/Energy loss indications. When Energy detector indicates Energy Loss, the link will be dropped.
Typical reaction time is 10µs
The Fast Link Down functionality allows the use of each of these options separately or in any combination.
Note that since this mode enables extremely quick reaction time, it is more exposed to temporary bad link-
quality scenarios.
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