DS3170 Maxim Integrated Products, DS3170 Datasheet - Page 81

• Manufacturer Part Number: DS3170
• Description: Network Controller & Processor ICs DS3-E3 Single-Chip T ransceiver T3-E3 Fra
• Manufacturer: Maxim Integrated Products

Figure 10-13. 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 10-14
Figure 10-14. DS3 Subframe Framer State Diagram
The multiframe framer checks for a multiframe boundary. When the multiframe framer identifies a multiframe
boundary, it updates the data path frame counters if either an OOF or OOMF condition is present. The multiframe
framer waits until a subframe boundary has been identified. Then, each bit position is checked for the multiframe
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
81 of 230
Load
F
F
F
F
F
F
F
13
23
33
43
53
63
73
DS3170 DS3/E3 Single-Chip Transceiver
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