XRT73LC03A Datasheet, PDF (43/61 Pages) Exar Corporation – 3 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT

XRT73LC03A
3 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
REV. 1.0.1
FIGURE 27. THE BEHAVIOR OF THE LOS OUTPUT INDICATOR IN RESPONSE TO THE LOSS OF SIGNAL AND THE RES-
TORATION OF SIGNAL
RTIP/
RRing
Actual Occurrence
of LOS Condition
Line Signal
is Restored
10 UI
255 UI
Time Range for
LOS Declaration
10 UI
255 UI
RLOS Output Pin
0 UI
G.775
Compliance
0 UI
Time Range for
LOS Clearance
G.775
Compliance
3.5.2 The LOS Declaration/Clearance Criteria
for DS3 and STS-1 Applications
When the XRT73LC03A is operating in the DS3 or
STS-1 Mode, then each channel declares and clears
LOS based upon the following two criteria.
• Analog LOS (ALOS) Declaration/Clearance Crite-
ria
• Digital LOS (DLOS) Declaration/Clearance Crite-
ria
In the DS3 Mode, the LOS output (RLOS) is simply
the logical "OR" of the ALOS and DLOS states.
1. The Analog LOS (ALOS) Declaration/Clearance
Criteria
A channel declares an Analog LOS (ALOS_(n)) Con-
dition if the amplitude of the incoming line signal
drops below a specific amplitude as defined by the
voltage at the LOSTHR input pin, and whether the
Receive Equalizer is enabled or not.
Table 5 presents the various voltage levels at the
LOSTHR input pin, the state of the Receive Equalizer
and the corresponding ALOS (Analog LOS) threshold
amplitudes.
TABLE 5: THE ALOS (ANALOG LOS) DECLARE AND CLEAR THRESHOLDS FOR A GIVEN SETTING OF LOSTHR &
REQEN (DS3 AND STS-1 APPLICATIONS)
APPLICATION
DS3
STS-1
REQEN SETTING
1
0
1
0
LOSTHR SETTING
1
1
1
1
SIGNAL LEVEL TO
DECLARE ALOS
<22mV
<17mV
<25mV
<20mV
SGNAL LEVEL TO CLEAR
ALOS
>90mV
>70mV
>115mV
>90mV
Declaring ALOS
A channel(n) declares ALOS_(n) whenever the ampli-
tude of the receive line signal falls below the Signal
Level to Declare ALOS levels, as specified inTable 5.
Clearing ALOS_(n)
A channel(n) clears ALOS_(n) whenever the ampli-
tude of the receive line signal increases above the
Signal Level to Clear ALOS levels, as specified in
Table 5.
There is approximately a 2dB hysteresis in the re-
ceived signal level that exists between declaring and
clearing ALOS_(n) in order to prevent chattering in
the RLOS_(n) output signal.
Monitoring the State of ALOS_(n)
41