![](http://datasheet.mmic.net.cn/Exar-Corporation/XRT79L71IB-F_datasheet_100145/XRT79L71IB-F_151.png)
PRELIMINARY
XRT79L71
136
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
NOTE:
This step configures the Transmit DS3/E3 Framer block to transmit an All Ones pattern, whenever the user
configures it to transmit the LOS Pattern.
STEP 2 - Set Bit 3 (TxLOS) within the Transmit DS3 Configuration Register to "1" as depicted below.
Once the user executes this step, then the Transmit DS3/E3 Framer block will override all of the outbound DS3
data payload and overhead bits, with an All Zeros pattern.
NOTE: When this bit is set, it overrides all of the other bits in this register.
4.2.5.2
TRANSMITTING THE DS3 AIS PATTERN
The Transmit DS3/E3 Framer block provides the user with two options associated with transmitting the DS3
AIS indicator.
Forced transmission of the DS3 AIS indicator (e.g., under software control)
Automatic transmission of the DS3 AIS indicator
Forced Transmission of the AIS Indicator
For DS3 Applications, the Transmit DS3/E3 Framer block permits the user to transmit either of the following
types of DS3 AIS patterns upon software control.
The Bellcore GR-499-CORE Standard DS3 AIS pattern which has the following characteristics.
a. A framed, repeating 1010… pattern
b. Valid M, F and P bits
c. All C-bits are set to "0".
The Relaxed Bellcore GR-499-CORE Standard DS3 AIS pattern which has the following characteristics
a. A framed, repeating 1010… pattern
b. Valid M, F and P bits
c. The C-bits are not necessarily set to "0"
The Unframed, All Ones Pattern
To force the Transmit DS3/E3 Framer block to transmit any one of these types of DS3 AIS patterns, the
following sequence of instructions must be executed.
Forcing the transmission of the Bellcore GR-499-CORE Compliant DS3 AIS pattern, upon Software
Control
The user can force the Transmit DS3/E3 Framer block to transmit the Bellcore GR-499-CORE Compliant DS3
AIS indicator upon software command by executing the following steps.
STEP 1 - Set Bit 6 (DS3 AIS Non-Stuck Stuff), within the Transmit DS3 Pattern Register to "0", as
depicted below.
Transmit DS3 Configuration Register (Address = 0x1130)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx Yellow
Alarm
Tx X-Bits
TxIdle
TxAIS
TxLOS
TxFERF
upon LOS
TxFERF
upon OOF
TxFERF
upon AIS
R/W
0
1