XRT7300
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E3/DS3/STS-1 LINE INTERFACE UNIT
REV. 1.1.1
3.6.2 The LOS Declaration/Clearance Criteria
for DS3 and STS-1 Applications
In the DS3 or STS-1 Modes the LOS output (RLOS)
is simply the logical OR of the ALOS and DLOS
states.
When the XRT7300 is operating in the DS3 or STS-1
Modes it declares and clears LOS based on either:
1. The Analog LOS (ALOS) Declaration/Clear-
ance Criteria
• Analog LOS (ALOS) Declaration/Clearance Criteria
or,
The XRT7300 declares an Analog LOS (ALOS) Con-
dition if the amplitude of the incoming line signal
drops below a specific amplitude as defined by the
state of the LOSTHR input pin.
• Digital LOS (DLOS) Declaration/Clearance Criteria
TABLE 4: THE ALOS DECLARATION AND CLEARANCE THRESHOLDS FOR A GIVEN SETTING OF LOSTHR (DS3 AND
STS-1 APPLICATIONS) FOR EQUALIZER ENABLED OR DISABLED
SIGNAL LEVEL TO DECLARE
SIGNAL LEVEL TO CLEAR
APPLICATION
LOSTHR SETTING
ALOS
ALOS
LOS LEVEL WITH EQUALIZER ENABLED
DS3
0
1
0
1
< 55mV
< 22mV
< 75mV
< 25mV
> 220mV
> 70mV
Sonet STS-1
> 270mV
> 110mV
LOS LEVEL WITH EQUALIZER DISABLED
DS3
0
1
0
1
< 35mV
< 17mV
< 55mV
< 20mV
> 155mV
> 70mV
> 210mV
> 90mV
Sonet STS-1
Declaring ALOS
in the contents of Command Register 0. The bit-for-
mat of Command Register 0 is presented below.
The XRT7300 declares an ALOS (Analog LOS) con-
dition whenever the amplitude of the input signal falls
below the Signal Level to Declare ALOS levels speci-
fied in Table 4.
COMMAND REGISTER CR0 (ADDRESS = 0X00)
D4
D3
D2
D1
D0
Clearing ALOS
RLOL
RLOS
ALOS
DLOS
DMO
The XRT7300 clears ALOS whenever the amplitude
of the input signal rises above the Signal Level to
Clear ALOS levels specified in Table 4.
Read
Only
Read
Only
Read
Only
Read
Only
Read
Only
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.
If the ALOS bit-field contains a “1”, the XRT7300 is
currently declaring an ALOS condition. If the ALOS
bit-field contains a “0”, the device is NOT currently de-
claring an ALOS condition.
Monitoring the State of ALOS
Disabling the ALOS Detector
If the XRT7300 is operating in the HOST Mode, the
state of ALOS can be polled or monitored by reading
It is useful to disable the ALOS Detector in the
XRT7300 for debugging purposes. If the XRT7300 is
operating in the HOST Mode, the ALOS Detector can
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