XRT73LC00A Datasheet, PDF (37/53 Pages) Exar Corporation – E3/DS3/STS-1 LINE INTERFACE UNIT

xr
PRELIMINARY
line signal. Figure 23 illustrates the LOS Declaration
and Clearance behavior in response to the first loss
XRT73LC00A
E3/DS3/STS-1 LINE INTERFACE UNIT
REV. P1.0.0
of signal event and then afterwards to the restoration
of the signal.
FIGURE 23. 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
3.6.2 The LOS Declaration/Clearance Criteria
for DS3 and STS-1 Applications
When the XRT73LC00A is operating in the DS3 or
STS-1 Modes it declares and clears LOS based on
either:
• Analog LOS (ALOS) Declaration/Clearance Criteria
or,
• Digital LOS (DLOS) Declaration/Clearance Criteria
In the DS3 or STS-1 Modes the LOS output (RLOS)
is simply the logical OR of the ALOS and DLOS
states.
1. The Analog LOS (ALOS) Declaration/Clear-
ance Criteria
The XRT73LC00A declares an Analog LOS (ALOS)
Condition if the amplitude of the incoming line signal
drops below a specific amplitude as defined by the
state of the LOSTHR input pin.
TABLE 4: THE ALOS (ANALOG LOS) DECLARE AND CLEAR THRESHOLDS FOR A GIVEN SETTING OF LOSTHR AND
REQEN FOR DS3 AND STS-1 APPLICATIONS
APPLICATION
REQEN SETTING
LOSTHR SETTING
SIGNAL LEVEL TO
DECLARE ALOS
SIGNAL LEVEL TO CLEAR
ALOS
DS3
1
1
<22mV
>90mV
0
1
<17mV
<70mV
STS-1
1
1
<25mV
>115mV
0
1
<20mV
<90mV
Declaring ALOS
The XRT73LC00A declares an ALOS (Analog LOS)
condition whenever the amplitude of the input signal
falls below the Signal Level to Declare ALOS levels
specified in Table 4.
Clearing ALOS
The XRT73LC00A clears ALOS whenever the ampli-
tude of the input signal rises above the Signal Level
to Clear ALOS levels specified in Table 4.
NOTE: There is approximately a 2dB hysteresis in the
received signal level that exists between declaring and
clearing ALOS in order to prevent chattering in the RLOS
output signal.
Monitoring the State of ALOS
34