XRT84L38IB Exar Corporation, XRT84L38IB Datasheet - Page 418

• 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
13.1.4.1
Message-Oriented signals (MOS) sent by the transmit LAPD Controller are messages conforming to ITU
Recommendation Q.921 LAPD protocol as defined below.
Two types of Message-Oriented signals are defined. One is a periodic performance report generated by the
source or sink T1/E1 terminals as defined by ANSI T1.403. The other is a path or test signal identification
message that may be optionally generated by a terminal or intermediate equipment on a T1/E1 circuit.
Message-oriented signals shall use the frame structure, field definitions and elements of procedure of the
LAPD protocol defined in ITU recommendation Q.921 except the address field. Performance information is
carried by Message-Oriented signal using LAPD protocol. The message structures of the periodic performance
report and path or test signal identification message are shown in
respectively.
13.1.4.1.1
The ANSI T1.403 standard requires that the status of the transmission quality be reported every one-second
interval. The one-second timing may be derived from the DS1 signal or from a separate equally accurate
(±32ppm) source. The phase of the one-second periods with respect to the occurrence of error events is
arbitrary; that is, the one-second timing does not depend on the time of occurrence of any error event. A total of
four seconds of information is transmitted so that recovery operations may be initiated in case an error corrupts
a message.
Counts of events shall be accumulated in each contiguous one-second interval. At the end of each one-second
interval, a modulo-4 counter shall be incremented, and the appropriate performance bits shall be set in bytes 5
and 6 in Format A. These octets and the octets that carry the performance bits of the preceding three one-
second intervals form the periodic performance report.
The periodic performance report is made up of 14 bytes of data. Bytes 1 to 4, 13, and 14 are the message
header and bytes 5 to 12 contain data regarding the four most-recent one-second intervals. The periodic
performance report message uses the SAPI/TEI value of 14.
F
IGURE
(second octet)
(high order)
Information
(low order)
(first octet)
Address
Address
Control
Flag
FCS
FCS
Flag
128. LAPD F
Discussion of MOS
0
0
8
Periodic Performance Report
1
1
7
RAME
Format A
One-second counts
1
1
6
SAPI
TEI
1
1
S
5
Flag
Flag
TRUCTURE
1
1
4
3
1
1
C/R
2
1
1
EA
EA
0
1
1 Octet
0
0
12
13
14
1
2
3
4
5
.
.
398
(second octet)
(high order)
Information
(low order)
(first octet)
Address
Address
Control
Flag
FCS
FCS
Flag
Figure 128
0
0
8
1
1
7
Format B
1
1
6
SAPI
in format A and format B
TEI
76 octets
1
1
5
Flag
Flag
1
1
4
3
1
1
C/R
2
1
1
EA
EA
REV. 1.0.1
0
1
1 Octet
0
0
80
81
82
1
2
3
4
5
.
.