XRT84L38IB Exar Corporation, XRT84L38IB Datasheet - Page 192

• 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
•
A CRC Multi-frame consists of 16 consecutive E1 frames, with the first of these frames being a FAS frame.
From a Frame Alignment point of view, the timeslot 0 octets of each of these E1 frames within the Multi-frame
are the most important 16 octets.
CRC Multi-frame.
Table 32
and Sub-Multi-Frame 2 is designated as SMF2.
SMF1 consists of E1 frames 0 through 7 consisting of 4 FAS frames and 4 non-FAS frames.
There are two interesting things to note in
frames are designated as C1, C2, C3 and C4. These four bit-fields contain the CRC-4 values which has been
computed over the previous SMF. Hence, while the Transmit E1 Framer is assembling a given SMF, it
computes the CRC-4 value for that SMF and inserts these results into the C1 through C4 bit-fields within the
very next SMF. These CRC-4 values ultimately are used by the Remote Receive E3 Framer for error-detection
purposes.
N
The second interesting thing to note regarding
FAS frames are of a fixed six (6) bit pattern: 0, 0, 1, 0, 1, 1; along with two bits, each designated at “E”. This six
bit pattern is referred to as the CRC Multi-Frame alignment pattern. This six-bit pattern will ultimately be used
by the Remote Receive E1 Framer for CRC Multi-Frame synchronization/alignment. Section discusses how
the Receive E1 Framer uses this 6-bit CRC Multi-frame alignment pattern for frame synchronization/alignment.
The "E" bits are used to indicate that the Local Receive E1 framer has detected errored sub-Multi-Frames.
2.2.1
2.2.2
OTE
CAS Multi-frame
SMF
: This framing structure is referred to as a CRC Multi-Frame because it permits the remote receiving terminal to
1
2
locate and verify the CRC-4 bit-fields.
has the CRC Multi-frame divided into 2 sub Multi-Frames. Sub-Multi-Frame 1 is designated as SMF1
The CRC Multi-frame Structure
CAS Multi-Frames and Channel Associated Signaling
N
F
UMBER
RAME
10
11
12
13
14
15
T
0
1
2
3
4
5
6
7
8
9
ABLE
32: B
B
C1
C2
C3
C4
C1
C2
C3
C4
IT
E
E
0
0
1
0
1
1
IT
0
F
ORMAT OF ALL
Table 32
B
IT
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1
Table 32
presents the bit-format for all timeslot 0 octets within a 16 frame
T
Table 32
B
IMESLOT
IT
A
A
A
A
A
A
A
A
0
0
0
0
0
0
0
0
2
. First, all of the bit-field 0 positions within each of the FAS
172
0
is that the bit-field 0 positions within each of the non-
OCTETS WITHIN A
B
Sa4
Sa4
Sa4
Sa4
Sa4
Sa4
Sa4
Sa4
IT
1
1
1
1
1
1
1
1
3
B
Sa5
Sa5
Sa5
Sa5
Sa5
Sa5
Sa5
Sa5
IT
1
1
1
1
1
1
1
1
4
CRC M
B
Sa6
Sa6
Sa6
Sa6
Sa6
Sa6
Sa6
Sa6
IT
0
0
0
0
0
0
0
0
ULTI
5
-
FRAME
B
Sa7
Sa7
Sa7
Sa7
Sa7
Sa7
Sa7
Sa7
IT
1
1
1
1
1
1
1
1
6
REV. 1.0.1
B
Sa8
Sa8
Sa8
Sa8
Sa8
Sa8
Sa8
Sa8
IT
1
1
1
1
1
1
1
1
7