Rainbow Electronics DS3170 - Manual (Page 84)

DS3170 DS3/E3 Single-Chip Transceiver
84 of 233
FEBE errors (C-bit format only) are determined by the C-bits in subframe four (C
41
, C
42
, and C
43
). A value of 111
indicates no error and any other value indicates an error.
The receive alarm indication (RAI) bit will be set high in the transmitter when one or more of the indicated alarm
conditions is present, and low when all of the indicated alarm conditions are absent. Setting the receive alarm
indication on LOS, SEF, LOF, or AIS is individually programmable (on or off).
The Application Identification Channel (AIC) is stored in a register bit. It is determined from the C
11
bit. The AIC is
set to one (C-bit format) if the C
11
bit is set to one in thirty-one consecutive multiframes. The AIC is set to zero (M23
format) if the C
11
bit is set to zero in four of the last thirty-one consecutive multiframes. Note: The stored AIC bit
must not change when an LOS, OOF, or AIS condition is present.
A FEBE is transmitted by default upon reception of a DS3 frame in which a C-bit parity error or a framing error is
detected and counted.
9.6.5 C-bit DS3 Framer/Formatter
9.6.5.1 Transmit C-bit DS3 Frame Processor
The C-bit DS3 frame format is shown in Figure 9-13 .
Figure 9-13. DS3 Frame Format
680 Bits
7 Sub-
Frames
X
1
X
2
P
1
P
2
M
1
M
2
M
3
F
11
F
21
F
31
F
41
F
51
F
61
F
71
F
12
F
22
F
32
F
42
F
52
F
62
F
72
F
13
F
23
F
33
F
43
F
53
F
63
F
73
F
14
F
24
F
34
F
44
F
54
F
64
F
74
C
11
C
21
C
31
C
41
C
51
C
61
C
71
C
12
C
22
C
32
C
42
C
52
C
62
C
72
C
13
C
23
C
33
C
43
C
53
C
63
C
73
Table 9-27 shows the function of each overhead bit in the DS3 Frame