xrt75r12 Exar Corporation, xrt75r12 Datasheet - Page 33

• Manufacturer Part Number: xrt75r12
• Description: Twelve Channel E3/ds3/sts-1 Line Interface Unit With Jitter
• Manufacturer: Exar Corporation

REV. 1.0.4
The Transmit Pulse Shaper converts the B3ZS encoded digital pulses into a single analog Alternate Mark
Inversion (AMI) pulse that meets the industry standard mask template requirements for STS-1 and DS3. For
E3 mode, the pulse shaper converts the HDB3 encoded pulses into a single full amplitude square shaped
pulse with very little slope. The Pulse Shaper Block also includes a Transmit Build Out Circuit, which can
either be disabled or enabled by setting the TxLEV_n bit to “1” or “0” in the control register. For DS3/STS-1
rates, the Transmit Build Out Circuit is used to shape the transmit waveform that ensures that transmit pulse
template requirements are met at the Cross-Connect system. The distance between the transmitter output and
the Cross-Connect system can be between 0 to 450 feet. For E3 rate, since the output pulse template is
measured at the secondary of the transformer and since there is no Cross-Connect system pulse template
requirements, the Transmit Build Out Circuit is always disabled. The differential line driver increases the
transmit waveform to appropriate level and drives into the 75 load as shown in
If the distance between the transmitter and the DSX3 or STSX-1, Cross-Connect system, is less than 225 feet,
enable the Transmit Build Out Circuit by setting the TxLEV_n control bit to “0”. If the distance between the
transmitter and the DSX3 or STSX-1 is greater than 225 feet, disable the Transmit Build Out Circuit.
F
F
4.4
4.4.1
IGURE
IGURE
19. HDB3 E
20. T
T
RANSMIT
TxLineClk(n)
TPDATA
Guidelines for using Transmit Build Out Circuit
TxNEG(n)
TxPOS(n)
Signal
RANSMIT
TClk
Line
TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR
P
ULSE
NCODING
P
ULSE
1
1
S
HAPER
0
0
S
F
HAPE
ORMAT
1
1
TPData(n)
TNData(n)
TxClk(n)
1
T
1
EST
0
0
C
IRCUIT
0
0
0
0
TRing(n)
TTIP(n)
30
0
V
1
1
0
0
31.6 +1%
31.6 + 1%
0
0
R1
R2
0
0
V
0
B
0
Figure
1:1
0
0
0
0
20.
75
R3
V
0
XRT75R12