XRT86VL38
PRELIMINARY
xr
OCTAL T1/E1/J1 FRAMER/LIU COMBO
REV. P1.0.6
393
When these interrupt enable bits are set and one or more Loss of Signals are present in the incoming DS1
frame, the XRT86VL38 framer will declare Receive Loss of Signal by doing the following:
•
Set the Receive Loss of Signal bit of the Alarm and Error Status Register to one indicating there is one or
more Loss of Signals. This status indicator is valid until the Framer Interrupt Status Register is read.
Reading this register clears the associated interrupt if Reset-Upon-Read is selected in Interrupt Control
Register (ICR). Otherwise, a write-to-clear operation by the microprocessor is required to reset these status
indicators.
The table below shows the Receive Loss of Signal status bits of the Alarm and Error Status Register.
11.5
E1 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 100 below shows the simple E1 system model.
ALARM AND ERROR STATUS REGISTER (AESR) (ADDRESS = 0XNB02H)
B
IT
N
UMBER
B
IT
N
AME
B
IT
T
YPE
B
IT
D
ESCRIPTION
4
Receive Loss of
Signal State
RUR /
WC
0 - There is no change of Loss of Signal state in the incoming DS1 payload
data.
1 - There is change of Loss of Signal state in the incoming DS1 payload
data.