XRT84L38IB Exar Corporation, XRT84L38IB Datasheet - Page 350

• Manufacturer Part Number: XRT84L38IB
• Description: Network Controller & Processor ICs 8 Ch T1/E1 Framer
• Manufacturer: Exar Corporation

Specifications of XRT84L38IB

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

XRT84L38
OCTAL T1/E1/J1 FRAMER
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.
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 XRT84L38 framer can generate two types of 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.
F
R
9.6.2
IGURE
EPEATER
Framed AIS
Unframed AIS
115. G
Framer Block
DS1 Transmit
Framer Block
DS1 Receive
How to configure the framer to transmit AIS
CO
ENERATION OF
The DS1 line is
Y
ELLOW
broken
A
LARM BY THE
Transmit
Receive
Section
Section
DS1
DS1
Repeater declares
Repeater
Red Alarm
internally
CPE
330
Transmit
Receive
Section
Section
UPON DETECTION OF
DS1
DS1
generate AIS to CO
Repeater detects
Yellow alarm and
Yellow
Alarm
AIS
AIS
ORIGINATED BY THE
DS1 Transmit
Framer Block
Framer Block
DS1 Receive
CPE
REV. 1.0.1