Rainbow Electronics DS3170 - Manual (Page 85)

DS3170 DS3/E3 Single-Chip Transceiver
85 of 233
Table 9-27. C-Bit DS3 Frame Overhead Bit Definitions
BIT DEFINITION
X
1
, X
2
Remote Defect Indication
(RDI)
P
1
, P
2
Parity Bits
M
1
, M
2
, and M
3
Multiframe Alignment Bits
F
XY
Subframe Alignment Bits
C
11
Application Identification
Channel (AIC)
C
12
Reserved
C
13
Far-End Alarm and Control
(FEAC) signal
C
21
, C
22
, and C
23
Unused
C
31
, C
32
, and C
33
C-bit parity bits
C
41
, C
42
, and C
43
Far-End Block Error (FEBE)
bits
C
51
, C
52
, and C
53
Path Maintenance Data Link
(or HDLC) bits
C
61
, C
62
, and C
63
Unused
C
71
, C
72
, and C
73
Unused
X
1
and X
2
are the Remote Defect Indication (RDI) bits (also referred to as the far-end SEF/AIS bits). P
1
and P
2
are
the parity bits used for line error monitoring. M
1
, M
2
, and M
3
are the multiframe alignment bits. F
XY
are the subframe
alignment bits. C
11
is the Application Identification Channel (AIC). C
12
is reserved for future network use, and has a
value of one. C
13
is the Far-End Alarm and Control (FEAC) signal. C
21
, C
22
, and C
23
are unused, and have a value
of one. C
31
, C
32
, and C
33
are the C-bit parity bits used for path error monitoring. C
41
, C
42
, and C
43
are the Far-End
Block Error (FEBE) bits used for remote path error monitoring. C
51
, C
52
, and C
53
are the path maintenance data link
(or HDLC) bits. C
61
, C
62
, and C
63
are unused, and have a value of one. C
71
, C
72
, and C
73
are unused, and have a
value of one. The X-bit, P-bit, M-bit, C-bit, and F-bit positions are overhead bits, and the other bit positions in the
T3 frame are payload bits regardless of how they are marked by TDEN.
9.6.5.2 Transmit C-bit DS3 Frame Generation
C-bit DS3 frame generation receives the incoming payload data stream, and overwrites all of the overhead bit
locations.
The multiframe alignment bits (M
1
, M
2
, and M
3
) are overwritten with the values zero, one, and zero (010)
respectively.
The subframe alignment bits (F
X1
, F
X2
, F
X3
, and F
X4
) are overwritten with the values one, zero, zero, and one (1001)
respectively.
The X-bits (X
1
and X
2
) are both overwritten with the Remote Defect Indicator (RDI). The RDI source is
programmable (automatic, 1, or 0). If the RDI is generated automatically, the X-bits are set to zero when one or
more of the indicated alarm conditions is present, and set to one when all of the indicated alarm conditions are
absent. Automatically setting RDI on LOS, SEF, LOF, or AIS is individually programmable (on or off).
The P-bits (P
1
and P
2
) are both overwritten with the calculated payload parity from the previous DS3 frame. The
payload parity is calculated by performing modulo 2 addition of all of the payload bits after all frame processing has
been completed. P-bit generation is programmable (on or off). The P-bits will be generated if either P-bit generation
is enabled or frame generation is enabled.
The bits C
11
, C
12
, C
21
, C
22
, C
23
, C
61
, C
62
, C
63
, C
71
, C
72
, and C
73
are all overwritten with a one.
The bit C
13
is overwritten with the Far-End Alarm and Control (FEAC) data input from the transmit FEAC controller.