
XRT75VL00
E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR
REV. 1.0.3
24
4.0
The Transmitter Section accepts TTL/CMOS level signals from the Terminal Equipment in the selectable data
formats.
In Single-Rail or un-encoded Non-Return-to-Zero (NRZ) input data via TPData pin while the TNData pin
must be grounded. The NRZ or Single-Rail mode is selected when the SR/DR
input pin is “High” (in
Hardware Mode) or bit 0 of the control register is “1” (in Host Mode). Figure 12 illustrates the Single-Rail or
NRZ format.
THE TRANSMITTER SECTION:
In Dual-Rail mode, data is input via TPData and TNData pins. TPData contains positive data and TNData
contains negative data. The SR/DR input pin = “Low” (in Hardware Mode) or bit 0 of the control register = “0”
(in Host Mode) enables the Dual-Rail mode. Figure 13 illustrates the Dual-Rail data format.
Convert the CMOS level B3ZS or HDB3 encoded data into pulses with shapes that are compliant with the
various industry standard pulse template requirements. Figure 7, Figure 8 and Figure 9 illustrate the pulse
template requirements.
Encode the un-encoded NRZ data into either B3ZS format (for DS3 or STS-1) or HDB3 format (for E3) and
convert to pulses with shapes and width that are compliant with industry standard pulse template
requirements. Figure 7,Figure 8 and Figure 9 illustrate the pulse template requirements.
4.1
T
RANSMIT
C
LOCK
:
The Transmit Clock applied via TxClk pin, for the selected data rate (for E3 = 34.368 MHz, DS3 = 44.736 MHz
or STS-1 = 51.84 MHz), is duty cycle corrected by the internal PLL circuit to provide a 50% duty cycle clock to
the pulse shaping circuit. This allows a 30% to 70% duty cycle Transmit Clock be supplied and thus eliminates
the need to use an expensive oscillator.
4.2
B3ZS/HDB3 E
NCODER
:
When the Single-Rail (NRZ) data format is selected, the Encoder Block encodes the data into either B3ZS
format (for either DS3 or STS-1) or HDB3 format (for E3).
4.2.1
B3ZS Encoding:
F
IGURE
12. S
INGLE
-R
AIL
OR
NRZ D
ATA
F
ORMAT
(E
NCODER
AND
D
ECODER
ARE
E
NABLED
)
F
IGURE
13. D
UAL
-R
AIL
D
ATA
F
ORMAT
(
ENCODER
AND
DECODER
ARE
DISABLED
)
TxClk
TPData
Data 1 1 0
TxClk
TPData
TNData
Data 1 1 0