XRT86VL38
PRELIMINARY
xr
OCTAL T1/E1/J1 FRAMER/LIU COMBO
REV. P1.0.6
405
11.6.1
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 XRT86VL38 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.
The Transmit Alarm Indication Signal Select bits of the Alarm Generation Register (AGR) enable the two types
of AIS transmission that are supported by the XRT86VL38 framer. The table below shows configurations of the
Transmit Alarm Indication Signal Select bits of the Alarm Generation Register (AGR)
F
IGURE
109. G
ENERATION
OF
Y
ELLOW
A
LARM
BY
THE
CPE
UPON
DETECTION
OF
AIS
ORIGINATED
BY
THE
R
EPEATER
DS1 Receive
Framer Block
DS1 Transmit
Framer Block
DS1 Receive
Framer Block
DS1 Transmit
Framer Block
DS1
Transmit
Section
DS1
Transmit
Section
DS1
Receive
Section
DS1
Receive
Section
CO
Repeater
CPE
The DS1 line is
broken
Repeater declares
Red Alarm
internally
Yellow
Alarm
Repeater detects
Yellow alarm and
generate AIS to CO
AIS