XRT73L04A Datasheet, PDF (35/65 Pages) Exar Corporation – 4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT

XRT73L04A
4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
REV. 2.0.3
FIGURE 18. AN EXAMPLE OF HDB3 ENCODING
TClk
TPOS
SR data
1 0 11
000001111011011001100001100100
Encoded
PDATA
1001000100101001001000100001000100
Encoded
NDATA
0010000001010010010001010010100000
Line signal
000 V
B0 0V
2.3.3 Disabling the HDB3/B3ZS Encoder
The XRT73L04A HDB3/B3ZS Encoder can be dis-
abled by two methods.
a. Operating in the Hardware Mode.
The HBD3/B3ZS Encoder blocks within all channels
are disabled by setting the CS/(SR/DR) input pin to
"1".
NOTE: By executing this step the HDB3/B3ZS Encoder and
Decoder blocks in all channels of the XRT73L04A are glo-
bally disabled.
a. Operating in the HOST Mode.
When the XRT73L04A is operating in the HOST
Mode, then the HDB3/B3ZS Encoders within each
channel can be individually enabled or disabled. Dis-
able the HDB3/B3ZS Encoder block within Chan-
nel(n) by setting the (SR/DR)_(n) bit-field within Com-
mand Register (CR3-(n)) to "1" as illustrated below.
COMMAND REGISTER CR3-(n)
D4
D3
D2
D1
D0
(SR/DR)_(n)
LOSMUT_(n)
RxOFF
RxClk_(n)INV
Reserved
1
X
X
X
X
NOTE: This method can only be used if the XRT73L04A is
operating in the HOST Mode.
If either of these methods are used to disable the
HDB3/B3ZS Encoder, then the LIU transmits the data
as received via the TPData_(n) and TNData_(n) input
pins.
2.4 THE TRANSMIT PULSE SHAPING CIRCUITRY
The Transmit Pulse Shaper Circuitry consists of a
Transmit Line Build-Out circuit which can be enabled
or disabled by setting the TxLEV_(n) input pin or
TxLEV_(n) bit-field to “High”or "Low". The purpose of
the Transmit Line Build-Out circuit is to permit config-
uration of each channel to transmit an output pulse
which is compliant to either of the following pulse
template requirements when measured at the Digital
Cross Connect System. Each of these Bellcore spec-
ifications state that the cable length between the
Transmit Output and the Digital Cross Connect sys-
tem can range anywhere from 0 to 450 feet.
The Isolated DSX-3 Pulse Template Requirement per
Bellcore GR-499-CORE is illustrated in Figure 19 and
the Isolated STSX-1 Pulse Template Requirement
per Bellcore GR-253-CORE is illustrated in Figure 20.
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