MT8910-1
12 ms
Superframe
Frame 1
Frame 2
Frame 3
Frame 4
1.5 ms
Frame
SW
2B + D
2B + D 2B + D
2B + D
2B + D
2B + D 2B + D
2B + D
Frame 5
Preliminary Information
Frame 6
Frame 7
Frame 8
2B + D 2B + D
2B + D 2B + D
M
Information
Channels
B11 B12 B13 B14
B15 B16 B17 B18 B21
B22 B23
B24 B25 B26
50
µs
B27 B28
D1
D2
50
µs
Corresponding
ST-BUS
12.5
µs
B7
B6
B5
B4
B3
B2
B1
B0
B7
B6
B5
B4
B3
B2
B1
B0
D0
D1
Figure 4 - Frame Structure
Basic Frame Synchronization (BFS) is achieved
using the algorithm shown in Figure 5. The DSLIC
searches for the sync word or the inverted sync word
within the received data stream. After detecting
three consecutive synchronization patterns spaced
exactly 120 quats apart, the DSLIC declares terminal
synchronization by setting the bits of the Internal
State Indicator to 111 in Status Register 1. A loss of
synchronization is declared by the DSLIC when at
least one of the nine quats at the beginning of each
Basic Frame differs by more than one quantization
level for two consecutive frames.
A search for superframe synchronization will begin
only after Basic Frame sync has been found. The
DSLIC will declare superframe sync (SFS) on the
first occurrence of the properly spaced Inverted Sync
Word (ISW) once Basic Frame sync has been
acquired. The synchronized state is identified by the
status of internal state bits IS2, IS1 and IS0 found in
Status Register 1.
The DSLIC will lose superframe sync under three
conditions;
1)
if the DSLIC loses basic frame sync,
2) if the ISW does not occur exactly eight basic
frames apart,
3)
if the ISW is received when it is not expected.
Activation/Deactivation
The DSLIC has a complete activation/deactivation
state machine which allows the user to activate or
deactivate the link as per the requirements in the
STATE : LOST
BFS
One
Valid
SW
:0
Error in
SW
> One-Level Error in SW
STATE : LOSING
BFS
:1
Error in
SW
Valid
SW
> One-Level
Error in SW
STATE : SENSING1
BFS
One
Valid
SW
STATE : SENSING2
BFS
: 0
One Valid SW
: 0
STATE : SYNC
BFS
:1
Figure 5 - Frame Synchronization State Diagram
9-8
MITEL [ MITEL NETWORKS CORPORATION ]
