XRT84L38IB Exar Corporation, XRT84L38IB Datasheet - Page 364

• 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
The table below shows configurations of the Receive Signaling Substitution Control [1:0] bits of the Receive
Signaling Control Register.
RECEIVE SIGNALING CONTROL REGISTER (RSCR) (INDIRECT ADDRESS = 0XN2H, 0X40H - 0X57H)
10.6
The XRT84L38 T1/J1/E1 Octal Framer can be configured to monitor quality of received DS1 frames. It can
generate error indicators 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 that can be detected by the XRT84L38
framer and error indications that will be generated.
10.6.1
As we discussed before, transmission of Alarm Indication Signal (AIS) or Blue Alarm by the intermediate node
indicates 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 detect two types of AIS in DS1 mode:
•
•
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 Alarm indication logic within the Receive Framer block of the XRT84L38 framer monitors the incoming
DS1 frames for AIS. AIS alarm condition are detected and declared according to the following procedure:
1. The incoming DS1 frames are monitored for AIS detection. AIS detection is defined as an unframed or
2. An AIS detection counter within the Receive Framer block of the XRT84L38 counts the occurrences of AIS
N
Framed AIS
Unframed AIS
UMBER
B
3-2
framed pattern with less than three zeros in two consecutive frames.
detection over a 6 ms interval. It will indicate a valid AIS flag when twenty-two or more of a possible twenty-
four AIS are detected.
IT
How to Configure the Framer to Detect Alarms and Error Conditions
How to configure the framer to detect AIS Alarm
Receive Signaling
Substitution
B
Control
IT
N
AME
B
IT
R/W
T
YPE
00 - The received signaling bits are replaced by all ones and send to the
external equipment.
01 - Two-code signaling substitution is applied to the received signaling
bits. The replaced signaling information is sent to the external equipment.
10 - Four-code signaling substitution is applied to the received signaling
bits. The replaced signaling information is sent to the external equipment.
11 - Sixteen-code signaling substitution is applied to the received signaling
bits. The replaced signaling information is sent to the external equipment.
N
OTE
: In SF mode, this option is disabled.
344
B
IT
D
ESCRIPTION
REV. 1.0.1