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XRT79L71
PRELIMINARY
165
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
This section presents the Jitter Transfer Characteristics of the XRT79L71, if the Jitter Attenuator PLL has been
enabled. As we present the Jitter Transfer Characteristics of the XRT79L71, we will also present some of the
various Jitter Transfer Characteristic requirements that the XRT79L71 complies with.
4.2.6.3
The Transmit Control Block
The purpose of the Transmit Control Block is to accept any of the following signals from the on-chip Registers,
and route the state of these signals to either the Transmit Pulse Shaping Block and the Line Driver block.
TxLEV - Transmit Line Build-Out Control
TAOS - Transmit All OneS Pattern
TxON - Transmit Driver ON/OFF
The role that TxLEV plays in the Transmit Pulse Shaping block is addressed in
Section 4.2.6.4. Similarly, the
role that TxON plays is address in
Section 4.2.6.5. However, none of these sections address the TAOS signal.
As a consequence, TAOS will be addressed in this section.
TAOS - Transmit All OneS
The user can configure the Transmit DS3/E3 LIU Block transmit an un-framed "All Ones" pattern via the TTIP
and TRING output pins. This can be accomplished by setting Bit 2 (TAOS), within the LIU Transmit Control
Register, to "1" as depicted below.
If the TAOS bit-field is set to "1", then the Transmit DS3/E3 LIU Block will overwrite the contents of the
outbound DS3 or E3 data-stream (that it receives from the Transmit DS3/E3 Framer block) with an unframed
All Ones pattern.
Conversely, if the TAOS bit-field is set to "0", then the Transmit DS3/E3 LIU Block will NOT overwrite the
contents of the outbound DS3 or E3 data-stream (that it receives from the Transmit DS3/E3 Framer block) with
an unframed All Ones pattern, as it transmit this DS3 or E3 data out onto the line.
4.2.6.4
The Transmit Pulse Shaping Block
For DS3 Applications, the purpose of the Transmit Pulse Shaping block is to permit the user to either enable or
disable the Transmit Line Build-Out circuitry within the Transmit DS3/E3 LIU Block. If the Transmit Line Build-
Out circuit is enabled, then it will provide some low-pass filtering of the transmit output pulses within the
outbound DS3 line signal, which will result in the transmission of some shaped (e.g., not square-wave) pulses
onto the DS3 line. In contrast, if the Transmit Line Build-Out circuit is disabled, then it will NOT provide any
low-pass filtering of the transmit output pulses. In this case, the Transmit DS3/E3 LIU Block will transmit
unshaped (somewhat square-shaped) pulses onto the line.
For DS3 Applications, the Transmit Line Build-Out circuit is used to shape the transmit output pulses within the
DS3 line signal such that these pulses with comply with the Isolated Pulse Template requirements per Bellcore
GR-499-CORE, when these pulses are measured at the DSX-3 location.
Guidelines for using the Transmit Line Build-Out Circuit
LIU Transmit Control Register (Address = 0x1304)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Internal
Transmit
Drive Moni-
tor
Unused
TAOS
Unused
TxLEV
R/O
R/W
R/O
R/W
R/O
R/W
0
1
0