
XRT84L38
171
REV. 1.0.1
OCTAL T1/E1/J1 FRAMER
The table above indicates that the FAS frame timeslot 0 octet consists of a single International Bit within bit-
field 0, Si, followed by a fixed 7-bit pattern within bit-fields 1 through 7.
B
IT
0—S
I
(I
NTERNATIONAL
B
IT
)
The Si bit within the FAS E1 Frame typically carries the results of a CRC-4 calculation, which is discussed in
greater detail in Section 2.2.1. The fixed framing pattern (e.g., 0, 0, 1, 1, 0, 1, 1) will be used by the Receive E1
Framer at the Remote terminal for frame synchronization/alignment purposes. Section discusses how the
Receive E1 Framer uses these bits.
Timeslot 0 octets within non-FAS frames
The bit-format of a timeslot 0 octet within a non-FAS frame is presented in
Table 31
.
The table above indicates the non-FAS frame timeslot 0 octet consists of a single international bit, Si, within bit-
field 0.
B
IT
0—S
I
(I
NTERNATIONAL
B
IT
)
The Si bit, within the non-FAS E1 Frame carries a specific value that will be used by the Receive E1 Framer, for
CRC Multi-frame alignment purposes. Section 7 discusses the exact role of the Si bit-field within the non-FAS
frames.
B
IT
1—F
IXED
AT
“1”
Bit-field “1” contains a fixed value “1”. This bit-field will be used for FAS framing synchronization/alignment
purposes by the Remote Receive E1 Framer. Section _ discusses how the Receive E1 Framer uses this bit-
field.
B
IT
2—A (FAS F
RAME
Y
ELLOW
A
LARM
B
IT
)
This bit-field is used to transmit a Yellow alarm to the Remote Terminal. This bit-field is set to “0” during normal
conditions, and is set to “1” whenever the Receive E1 Framer detects an LOS (Loss of Signal) or LOF (Loss of
Framing) condition in the incoming E1 frame data.
B
IT
3
THROUGH
7—S
A
4–S
A
8 (N
ATIONAL
B
ITS
)
These bit-fields can be used to carry data link information from the Local transmitting terminal to the Remote
receiving terminal. Since the National bits only exist in the non-FAS frames, they offer a maximum signaling
data link bandwidth of 20kbps.
2.2
The E1 Multi-frame Structures
The 84L38 Octal Framer supports two kinds of E1 Multi-frame structures:
CRC Multi-frame
T
ABLE
31: B
IT
F
ORMAT
OF
T
IMESLOT
0
OCTET
WITHIN
A
N
ON
-FAS E1 F
RAME
B
IT
7
6
5
4
3
2
1
0
Value
Sa8
Sa7
Sa6
Sa5
Sa4
A
1
Si
Function6
National bits
Yellow Alarm
Fixed Value
International Bit
Description-
Operation
National Bits
These bit-fields can be used
to carry data link information
from the Local transmitting
terminal to the Remote
receiving terminal. Since the
National bits only exist in the
non-FAS frames, they offer a
maximum signaling data link
bandwidth of 20kbps.
FAS Frame Yellow Alarm Bit
This bit-field is used to transmit
a Yellow alarm to the Remote
Terminal. This bit-field is set to
“0” during normal conditions,
and is set to “1” whenever the
Receive E1 Framer detects an
LOS (Loss of Signal) or LOF
(Loss of Framing) condition in
the incoming E1 frame data.
Fixed at “1”
Bit-field “1” contains a
fixed value “1”. This bit-
field will be used for FAS
framing synchronization/
alignment purposes by the
Remote Receive E1
Framer.
International Bit
The Si bit within the non-FAS
E1 Frame typically carries a
specific value that will be
used by the Receive E1
Framer for CRC Multi-frame
alignment purposes.