ds3171n Maxim Integrated Products, Inc., ds3171n Datasheet - Page 80

• Manufacturer Part Number: ds3171n
• Description: Ds3171, Ds3172, Ds3173, Ds3174 Single/dual/triple/quad Ds3/e3 Single-chip Transceivers
• Manufacturer: Maxim Integrated Products, Inc.

Figure 10-14. DS3 Frame Format
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. Refer to
Figure 10-15
Figure 10-15. DS3 Subframe Framer State Diagram
M
M
M
X
X
P
P
1
2
1
2
1
2
3
Verify
F
F
F
F
F
F
F
for the subframe framer state diagram.
11
21
31
41
51
61
71
C
C
C
C
C
C
C
11
21
31
41
51
61
71
All 4 bit positions failed
2 F-bits loaded
Sync
F
F
F
F
F
F
F
12
22
32
42
52
62
72
680 Bits
C
C
C
C
C
C
C
12
22
32
42
52
62
72
Load
80
F
F
F
F
F
F
F
13
23
33
43
53
63
73
C
C
C
C
C
C
C
13
23
33
43
53
63
73
F
F
F
F
F
F
F
14
24
34
44
54
64
74
7 Sub-
Frames