XRT86L30
REV. 1.0.1
SINGLE T1/E1/J1 FRAMER/LIU COMBO
loss of incoming signal. The Figure below illustrates this scenario in which the Repeater is sending an AIS to
the CPE and the CPE is sending a Yellow Alarm back to the Repeater.
FIGURE 106. GENERATION OF
YELLOW
A
LARM BY THE CPE UPON DETECTION OF AIS ORIGINATED BY THE
R
EPEATER
Repeater declares
Red Alarm
internally
CO
Repeater
CPE
Yellow
Alarm
DS1
Transmit
Section
DS1
Receive
Section
DS1 Receive
Framer Block
DS1 Receive
Framer Block
AIS
DS1
Receive
Section
DS1
Transmit
Section
DS1 Transmit
Framer Block
DS1 Transmit
Framer Block
The DS1 line is
broken
Repeater detects
Yellow alarm and
generate AIS to CO
12.6.1
How to configure the framer to transmit AIS
As we discussed in the previous section, Alarm Indication Signal (AIS) or Blue Alarm is transmitted by the
intermediate node to indicate that the equipment is still functioning but unable to offer services. It is an all ones
(except for framing bits) pattern which can be used by the equipment further down the line to maintain clock
recovery and timing synchronization.
The XRT86L30 framer can generate two types of AIS:
•
•
Framed AIS
Unframed AIS
Unframed AIS is an all ones pattern. If unframed AIS is sent, the equipment further down the line will be able to
maintain timing synchronization and be able to recover clock from the received AIS signal. However, due to the
lack of framing bits, the equipment farther down the line will not be able to maintain frame synchronization and
will declare Loss of Frame (LOF).
On the other hand, the payload portion of a framed AIS pattern is all ones. However, a framed AIS pattern still
has correct framing bits. Therefore, the equipment further down the line can still maintain frame
synchronization as well as timing synchronization. In this case, no LOF or Red alarm will be declared.
242
EXAR [ EXAR CORPORATION ]
