
XRT84L38
363
REV. 1.0.1
OCTAL T1/E1/J1 FRAMER
11.5
How to Configure the XRT84L38 Framer to Generate and Transmit Alarms and Error Indications
to Remote Terminal
The XRT84L38 T1/J1/E1 Octal Framer can be configured to monitor quality of received E1 frames. It can
generate error indications if the local receive framer has received error frames from the remote terminal. If
corresponding interrupt is enabled, the local microprocessor operation is interrupted by these error conditions.
Upon microprocessor interruption, the user can intervene by looking into the error conditions.
At the same time, the user can configure the XRT84L38 framer to transmit alarms and error indications to
remote terminal. Different alarms and error indications will be transmitted depending on the error condition.
The section below gives a brief discussion of the error conditions and appropriate alarms that should be
generated and transmitted by the XRT84L38 framer.
11.5.1
Brief discussion of alarms and error conditions
As defined in E1 specification, alarm conditions are created from defects. Defects are momentary impairments
present on the E1 trunk. If a defect is present for a sufficient amount of time (called the integration time), then
the defect becomes an alarm. Once an alarm is declared, the alarm is present until after the defect clears for a
sufficient period of time. The time it takes to clear an alarm is called the de-integration time.
Alarms are used to detect and warn maintenance personnel of problems on the E1 trunk. There are three
types of alarms:
Red alarm or Service Alarm Indication (SAI) Signal
Blue alarm or Alarm Indication Signal (AIS)
Yellow alarm or Remote Alarm Indication (RAI) Signal
To explain the error conditions and generation of different alarms, let us create a simple E1 system model. In
this model, an E1 signal is sourced from the Central Office (CO) through a Repeater to the Customer Premises
Equipment (CPE). At the same time, an E1 signal is routed from the CPE to the Repeater and back to the
Central Office.
Figure 119
below shows the simple E1 system model.
When the E1 system runs normally, that is, when there is no Loss of Signal (LOS) or Loss of Frame (LOF)
detected in the line, no alarm will be generated. Sometimes, intermittent outburst of electrical noises on the line
might result in Bipolar Violation or bit errors in the incoming signals, but these errors in general will not trigger
F
IGURE
119. S
IMPLE
D
IAGRAM
OF
E1
SYSTEM
MODEL
E1 Receive
Framer Block
E1 Transmit
Framer Block
E1 Receive
Framer Block
E1 Transmit
Framer Block
E1
Transmit
Section
E1
Transmit
Section
E1
Receive
Section
E1
Receive
Section
CO
Repeater
CPE
Simple E1 System Model