XRT73L03 Datasheet, PDF (44/62 Pages) Exar Corporation – 3 CHANNEL E3/DS3/STS-1 LINE INTERFCE UNIT

XRT73L03 3 CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT
REV. P1.0.13
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PRELIMINARY
Disabling the ALOS Detector
For debugging purposes it may be useful to disable
the ALOS Detector in the XRT73L03. If the
XRT73L03 is operating in the HOST Mode the ALOS
Detector can be disabled by writing a "1" into the
ALOSDIS(n) bit-field in Command Register CR2.
COMMAND REGISTER CR2-(N)
D4
D3
D2
D1
D0
Reserved
ENDECDIS(n)
ALOSDIS(n)
DLOSDIS(n)
REQEN(n)
X
X
1
X
X
2. The Digital LOS (DLOS) Declaration/Clearance
Criteria
COMMAND REGISTER CR0-(N)
A given Channel(n) in the XRT73L03 declares a Digi-
tal LOS (DLOS(n)) condition if the XRT73L03 detects
160±32 or more consecutive "0’s" in the incoming da-
ta.
The channel clears DLOS if it detects four consecu-
tive sets of 32 bit-periods, each of which contains at
least 10 "1’s" (e.g., average pulse density of greater
than 33%).
Monitoring the State of DLOS
If the XRT73L03 is operating in the HOST Mode the
state of DLOS(n) of Channel(n) can be polled or mon-
itored by reading in the contents of Command Regis-
ter CR0.
D4
D3
D2
D1
D0
RLOL(n) RLOS(n) ALOS(n) DLOS(n) DMO(n)
Read Only Read Only Read Only Read Only Read Only
If the DLOS(n) bit-field contains a “1”, then the corre-
sponding Channel(n) is currently declaring a DLOS
condition. If the DLOS(n) bit-field contains a “0”, the
Channel(n) is currently declaring the DLOS condition.
Disabling the DLOS Detector
For debugging purposes, it is useful to be able to dis-
able the DLOS(n) detector in the XRT73L03. If the
XRT73L03 is operating in the HOST Mode the DLOS
Detector can be disabled by writing a “1” into the
DLOSDIS(n) bit-field of Command Register CR2.
COMMAND REGISTER CR2-(N)
D4
D3
D2
D1
D0
Reserved
ENDECDIS(n)
ALOSDIS(n)
DLOSDIS(n)
REQEN(n)
X
X
X
1
X
NOTE: Setting both the ALOSDIS(n) and DLOSDIS(n) bit-
fields to "1" disables LOS Declaration by Channel(n).
3.5.3 Muting the Recovered Data while the LOS
is being Declared
In some applications it is not desirable for a channel
of the XRT73L03 to recover data and route it to the
Receiving Terminal while the channel is declaring an
LOS condition. Consequently, the XRT73L03 in-
cludes an LOS Muting feature. This feature if en-
abled causes a given channel to halt transmission of
the recovered data to the Receiving Terminal while
the LOS condition is "true". In this case, the RPOS(n)
and RNEG(n) output pins are forced to "0". Once the
LOS condition has been cleared, the channel re-
sumes normal transmission of the recovered data to
the Receiving Terminal.
This feature is available whenever the XRT73L03 is
operating in the HOST or Hardware Mode.
a. Operating in the Hardware Mode.
To enable the MUTing upon LOS feature for all chan-
nels of the XRT73L03, pull the LOSMUTEN output
pin (pin 78) "High".
b. Operating in the HOST Mode.
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