
PEB 3445 E
Functional Description
Data Sheet
48
2001-06-29
4.5.2
The framing structure of the C-bit parity format is shown in
Table 3
. The assignment of
the information bits [84] is identical to the M23 multiplex format, but the function of the
C-bits is redefined for path maintenance and data link channels.
C-bit parity format
Table 4
C-bit parity format
F
0
, F
1
F
0
and F
1
form the frame alignment pattern. Each DS3 frame consists of 28 F-bits, four per
subframe in block 2, 4, 6 and 8. F
0
and F
1
form the pattern ’1001’. This pattern is repeated in
every subframe.
M
0
, M
1
M
0
and M
1
form the multiframe alignment signal. The M-bit is contained in the OH-bit of the first
block in subframe 5,6 and 7. The multiframe alignment signal is ’010’.
N
r
Reserved. Set to ’1’ in transmit direction.
AIC
Application Identification Channel.
DL
t
The terminal-to-terminal path maintenance data link uses the HDLC protocol. Access to the DL
t
bits is possible via the integrated signalling controller.
DL
Reserved. Access to the DL-bits is possible via the spare bit registers.
FEAC
The alarm or status information of a far end terminal is sent back over the far end and control
channel. This bit also contains DS3 or DS1 line loopback requests. Messages are sent in bit
oriented mode. The far end alarm and control channel can be accessed via the internal signalling
controller.
Sub-
frame
Block 1 through 8 of a subframe
3
4
1
2
5
6
7
8
DS3-
Multi-
frame
1
2
3
4
5
6
7
X [84] F
1
[84] AIC [84] F
0
[84] N
r
[84] F
0
[84]
FEAC
[84] F
1
[84]
X [84] F
1
[84] DL [84] F
0
[84] DL [84] F
0
[84] DL [84] F
1
[84]
P [84] F
1
[84] CP [84] F
0
[84] CP [84] F
0
[84] CP [84] F
1
[84]
P [84] F
1
[84]
FEBE
[84] F
0
[84]
FEBE
[84] F
0
[84]
FEBE
[84] F
1
[84]
M
0
[84] F
1
[84] DL
t
[84] F
0
[84] DL
t
[84] F
0
[84] DL
t
[84] F
1
[84]
M
1
[84] F
1
[84] DL [84] F
0
[84] DL [84] F
0
[84] DL [84] F
1
[84]
M
0
[84] F
1
[84] DL [84] F
0
[84] DL [84] F
0
[84] DL [84] F
1
[84]