Siemens CC-2M Directions For Use Manual page 42

English
E1 / T1 Frame structure
The timeslots for the E1 frame are counted from 0 to 31 and for the T1 frame from 1 to 24.
The multiframe structure is used in the E1 mode. This structure is composed of 16 single
frames. The timeslots 0 and 16 are not used for the transmission of user data. The structure
of the timeslots 0 and 16 corresponds to the specifications of the standard G.732/G.704.
Timeslot 0 is used for synchronisation and alarm transport. Timeslot 16 is reserved for
signalling.
At the receiver side the CC–2M recognises frames with and without CRC–4. Provided that
it exists, the CRC is evaluated by the CC–2M and will be inserted as E–Bits into transmit
frame.
At the receiver side the E–bits are not evaluated. There will be no external signalling over
the condition of the CRC.
The following table shows the assignment of the timeslot 0. The first bit is used for CRC in
the case of even frames and for the identification of a multiframe and the E-bits in the case
of uneven frames. The second bit indicates whether it is an even or uneven frame (1 =
uneven, 0 = even). Bits 3 to 8 of any even frame are reserved for synchronisation (011011).
The S-bits are not used and have been set to "0". The A–bit indicates an error such as LOF
(Loss of Frame), LOS (Loss of Signal) and AIS (Alarm Indication Signal). When there is an
alarm, the A–bit is set to "1", otherwise to "0".
Sub- Frame
Multi- No.
frame
0
1
2
3
1
4
5
6
7
8
9
10
11
2
12
13
14
15
S = S pare Bit
A = A larm Bit (Remote Alarm indication)
C = C RC Bit
E = CRC–4 E rror indication bits
42
1 2
C1 0
0 1
C2 0
0 1
C3 0
1 1
C4 0
0 1
C1 0
1 1
C2 0
1 1
C3 0
E 1
C4 0
E 1
Bit No.
3 4 5
0 1 1
A S S
0 1 1
A S S
0 1 1
A S S
0 1 1
A S S
0 1 1
A S S
0 1 1
A S S
0 1 1
A S S
0 1 1
A S S
7XV5662-0AD00
6 7 8
0 1 1
S S S
0 1 1
S S S
0 1 1
S S S
0 1 1
S S S
0 1 1
S S S
0 1 1
S S S
0 1 1
S S S
0 1 1
S S S
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