![](http://datasheet.mmic.net.cn/Maxim-Integrated-Products/DS3164-_datasheet_97074/DS3164-_161.png)
DS3161/DS3162/DS3163/DS3164
the multiframe alignment bits M1, M2, and M3, which have a value of zero, one, and zero respectively. The DS3
framer is an off-line framer that only updates the data path frame counters when either an out of frame (OOF) or an
out of multiframe (OOMF) condition is present. The use of an off-line framer reduces the average time required to
reframe, and reduces data loss caused by burst error. The DS3 framer has a Maximum Average Reframe Time
(MART) of approximately 1.0 ms.
Figure 10-38. 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
The subframe framer continually searches four adjacent bit positions for a subframe boundary. A subframe
alignment bit (F-bit) checker checks each bit position. All four bit positions must fail before any other bit positions
are checked for a subframe boundary. There are 170 possible bit positions that must be checked, and four
positions are checked simultaneously. Therefore, up to 43 checks may be needed to identify the subframe
boundary. The subframe framer enables the multiframe frame once it has identified a subframe boundary. See