XRT73L00A Datasheet, PDF (28/53 Pages) Exar Corporation – E3/DS3/STS-1 LINE INTERFACE UNIT

XRT73L00A
E3/DS3/STS-1 LINE INTERFACE UNIT
REV. 2.0.1
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2.3.3 Enabling/Disabling the HDB3/B3ZS
Encoder
The XRT73L00A allows two methods to enable or
disable the HDB3/B3ZS Encoder.
If the XRT73L00A is operating in the Hardware
Mode.
To enable the HDB3/B3ZS Encoder, set the ENDEC-
DIS input pin (pin 21) to “0”. To disable the HDB3/
B3ZS Encoder, set the ENDECDIS input pin (pin 21)
to “1”.
If the XRT73L00A is operating in the HOST Mode.
To enable the HDB3/B3ZS Encoder, set the ENDEC-
DIS bit-field in Command Register (CR2) to “0”.
COMMAND REGISTER CR2 (ADDRESS = 0X02)
D4
D3
D2
D1
D0
Reserved ENDECDIS ALOSDIS DLOSDIS REQDIS
X
0
X
X
X
To disable the HDB3/B3ZS Encoder, set the ENDEC-
DIS bit-field in Command Register (CR2) to “1”.
If either of these two methods is employed to disable
the HDB3/B3ZS Encoder, the LIU transmits the data
onto the line as it is received via the TPDATA and
TNDATA input pins.
2.4 THE TRANSMIT PULSE SHAPER CIRCUITRY
The Transmit Pulse Shaper Circuitry consists of a
Transmit Line Build-Out circuit which can be enabled
or disabled by setting the TXLEV input pin or bit-field
to “High” or “Low”. The purpose of the Transmit Line
Build-Out circuit is to permit configuring of the
XRT73L00A to transmit an output pulse which is com-
pliant to either of the following Bellcore pulse tem-
plate requirements when measured at the Digital
Cross Connect System. Each of these Bellcore spec-
ifications further state that the cable length between
the Transmit Output and the Digital Cross Connect
system can range anywhere from 0 to 450 feet.
The Isolated DSX-3 Pulse Template Requirement per
Bellcore GR-499-CORE is illustrated in Figure 7.
The Isolated STSX-1 Pulse Template Requirement
per Bellcore GR-253-CORE is illustrated in Figure 8.
2.4.1 Enabling the Transmit Line Build-Out Cir-
cuit
If the Transmit Line Build-Out Circuit is enabled, the
XRT73L00A outputs shaped pulses onto the line via
the TTIP and TRING output pins.
Do the following to enable the Transmit Line Build-Out
circuit in the XRT73L00A:
• If the XRT73L00A is operating in the Hardware
Mode, set theTXLEV input pin (pin 1) to “Low”
• If the XRT73L00A is operating in the HOST Mode,
set the TXLEV bit-field to “0” as illustrated below.
COMMAND REGISTER CR1 (ADDRESS = 0X01)
D4
D3
D2
D1
D0
TXOFF TAOS TXCLKINV TXLEV TXBIN
0
X
X
0
X
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