XRT73L04B
4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
REV. 1.0.1
28
2.0
THE TRANSMIT SECTION
Figure 13 indicates that the Transmit Section within
each Channel of the XRT73L04B consists of the fol-
lowing blocks:
• Transmit Logic Block
• TxClk_(n) Duty Cycle Adjust Block
• HDB3/(B3ZS) Encoder
• Pulse Shaping Block
The purpose of the Transmit Section is to take TTL/
CMOS level data from the terminal equipment and
encode it into a format such that it can:
1. Be efficiently transmitted over coaxial cable at
E3, DS3, or STS-1 data rates.
2. Be reliably received by the Remote Terminal
Equipment at the other end of the E3, DS3, or
STS-1 data link.
3. Comply with the applicable pulse template
requirements.
2.1
T
HE
T
RANSMIT
L
OGIC
B
LOCK
The purpose of the Transmit Logic Block is to accept
either Dual-Rail or Single-Rail (e.g., a binary data
stream) TTL/CMOS level data and timing information
from the Terminal Equipment.
2.1.1
Accepting Dual-Rail Data from the Termi-
nal Equipment
Whenever the XRT73L04B accepts Dual-Rail data
from the Terminal Equipment, it does so via the fol-
lowing input signals:
• TPData_(n)
• TNData_(n)
• TxClk_(n)
Figure 14 illustrates the typical interface for the trans-
mission of data in a Dual-Rail Format between the
Terminal Equipment and the Transmit Section of the
XRT73L04B.
The manner that the LIU handles Dual-Rail data is
described below and illustrated in Figure 15. The
Transmit Section (of a Channel) typically samples the
data on the TPData_(n) and TNData_(n) input pins
on the falling edge of TxClk_(n).
F
IGURE
14. T
HE
TYPICAL
INTERFACE
FOR
THE
T
RANSMISSION
OF
D
ATA
IN
A
D
UAL
-R
AIL
F
OR
-
MAT
FROM
THE
T
RANSMITTING
T
ERMINAL
E
QUIPMENT
TO
THE
T
RANSMIT
S
ECTION
OF
A
CHANNEL
Terminal
Equipment
(E3/DS3 or STS-1
Framer)
Exar E3/DS3/STS-1 LIU
Transmit
Logic
Block
TxPOS
TxNEG
TxLineClk
TPData
TNData
TxClk
F
IGURE
15. T
HE
XRT73L04B S
AMPLES
THE
DATA
ON
THE
TPD
ATA
AND
TND
ATA
INPUT
PINS
TxClk
TPData
TNData
Data 1 1 0
