GS3140 Datasheet, PDF (14/40 Pages) Semtech Corporation – Multi-Rate Adaptive 3G SDI Equalizer

4.5 Loss of Signal (LOS)
The Loss of Signal (LOS) status indicates whether or not a signal that meets the device‘s
programmed thresholds is present at its input. When LOS is de-asserted (set to 0), a
supported input signal has been detected. Figure 4-1 shows how LOS is derived.
The LOS function continuously monitors conditions of the input signal. In Sleep,
Auto-Sleep, Bypass or Auto-Bypass modes, this is limited to carrier detection.
When LOS Filter is disabled, LOS will be asserted (set to 1) no less than 10μs and no
longer than 40μs after the loss of a valid input signal, and will be de-asserted (set to 0)
no more than 5μs after the connection of a valid input signal.
LOS is available via a status bit in STATUS_REG_0, and it is also available on the interrupt
(INT) status pin, as selected using the INT_SOURCE_SELECT bits in
INT_OUT_CONF_REG_0 register accessible through the device‘s host interface. LOS is
the default output from the INT pin.
4.5.1 Programmable LOS Filter
The LOS Filter delays notification of the change in raw LOS until the new state persists
contiguously for the programmed length of time. This increases stability of LOS
signalling.
The LOS Filter assertion and de-assertion delays can be programmed through the
GS3140 host interface. By default, the LOS Filter is set to 51.8μs assertion delay and
6.6ms de-assertion delay.
The LOS assertion delay can be set in the range from 0ms to 6.6ms in increments of
25.9μs. The LOS de-assertion delay can be set in the range of 0s to 1.7s in increments of
6.6ms. These parameters are accessible using the LOS_FILTER_SET_DELAY and
LOS_FILTER_CLEAR_DELAY bits in LOS_FILTER_CONF_REG_0
The use of these parameters can be disabled using the LOS_FILTER_DISABLE bit in
LOS_FILTER_CONF_REG_1. Figure 4-1 below shows the derivation of the LOS status
indication, and how the LOS filter affects the output.
Set to 1 when any of the following:
SLEEP, AUTO_SLEEP, BYPASS, AUTO BYPASS
Carrier Detect
1
Combination of Carrier Detect
0
and Squelch
Raw LOS
LOS Filter
LOS_FILTER_DISABLE
LOS_FILTER_SET_DELAY
LOS_FILTER_CLEAR_DELAY
Figure 4-1: Factors Affecting the Assertion of the LOS Status Parameter
LOS (Status Parameter)
GS3140
Final Data Sheet
PDS-060939
Rev.1
May 2015
www.semtech.com
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