á
XRT7300
E3/DS3/STS-1 LINE INTERFACE UNIT
REV. 1.1.1
23
Figure 14 illustrates the HDB3 Encoder at work with
two separate strings of four (or more) consecutive ze-
ros.
2.3.3
Encoder
The XRT7300 allows two methods to enable or dis-
able the HDB3/B3ZS Encoder.
If the XRT7300 is operating in the Hardware Mode.
To enable the HDB3/B3ZS Encoder, set the ENCO-
DIS input pin (pin 21) to “0”. To disable the HDB3/
B3ZS Encoder, set the ENCODIS input pin (pin 21) to
“1”.
If the XRT7300 is operating in the HOST Mode.
To enable the HDB3/B3ZS Encoder, set the ENCO-
DIS bit-field in Command Register (CR2) to “0”.
Enabling/Disabling the HDB3/B3ZS
To disable the HDB3/B3ZS Encoder, set the ENCO-
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
T
HE
T
RANSMIT
P
ULSE
S
HAPER
C
IRCUITRY
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 TXLEV
bit-field) to “High” or “Low”. The purpose of the
Transmit Line Build-Out circuit is to permit configuring
of the XRT7300 to transmit an output pulse which is
compliant to either of the following Bellcore pulse
template 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
XRT7300 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 XRT7300:
If the XRT7300 is operating in the Hardware Mode,
set theTXLEV input pin (pin 1) to “Low”
If the XRT7300 is operating in the HOST Mode, set
the TXLEV bit-field to “0” as illustrated below.
2.4.2
cuit
Disabling the Transmit Line Build-Out Cir-
F
IGURE
14. A
N
E
XAMPLE
OF
HDB3 E
NCODING
Data
TPDATA
TNDATA
1 0 1 1 0 0 0 0 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 0 0 0 0 1
0 0 0 V
Line Signal
B 0 0 V
TCLK
COMMAND REGISTER CR2 (ADDRESS = 0X02
D4
D3
D2
D1
D0
DECODIS ENCODIS ALOSDIS DLOSDIS
REQDIS
X
0
X
X
X
COMMAND REGISTER CR1 (ADDRESS = 0X01)
D4
D3
D2
D1
D0
TXOFF
TAOS
TXCLKINV
TXLEV
TXBIN
0
X
X
0
1