MT90863
F0i
(HMVIP Frame)
C4i/C8i
(4.096MHz)
C16i
Advance Information
F0o
C4o
Channel 0
STio 0 - 15
STi/STo 0 - 15
(2Mb/s mode)
STio 16 - 23
(8Mb/s mode)
1
0
7
Channel 0
0
7
6
5
4
3
2
1
0
6
5
6
1
Channel 127
4
3
2
1
0
7
Channel 31
0
7
Channel 0
STi12/STo12
(Sub-rate
Switching)
0
1
0
1
Channel 127
0
Bit 1
Figure 6- HMVIP Mode Timing for 2 and 8 Mb/s Data Streams
Backplane Interface
The backplane interface can be programmed to
accept data streams of 2Mb/s, 4Mb/s or 8Mb/s.
When 2Mb/s mode is enabled, STio0 to STio31 have
a data rate of 2.048Mb/s. When 4Mb/s mode is
enabled, STio0 to STio31 have a data rate of
4.096Mb/s. When 8Mb/s mode is enabled, STio0 to
STio15 have a data rate of 8.192Mb/s. When HMVIP
mode is enabled, STio0 to STio15 have a data rate
of 2.048Mb/s and STio16 to STio23 have a data rate
of 8.192Mb/s.
Table 2 describes the data rates and mode selection
for the backplane interface.
Local Interface
Three operation modes, 2Mb/s, 8Mb/s and Sub-rate
Switching mode, can be selected for the local
interface. When 2Mb/s mode is selected, STi0 to
STi15 and STo0 to STo15 have a 2.048Mb/s data
rate. When 8Mb/s mode is selected, STi0 to STi3
and STo0 to STo3 have an 8.192Mb/s data rate.
When Sub-rate Switching mode is selected, STi0 to
STi11 and STo0 to STo11 have 2.048Mb/s data with
64kb/s data channels and STi12 and STo12 have a
2.048Mb/s data rate with 16kb/s data channels.
Table 3 describes the data rates and mode selection
for the local interface.
Input Frame Offset Selection
Input frame offset selection allows the channel
alignment of individual backplane input streams, that
8
operate at 8.192Mb/s (STio0-23), to be shifted
against the input frame pulse (F0i). This feature
compensates for the variable path delays caused by
serial backplanes of variable length. Such delays can
be occur in large centralized and distributed
switching systems.
Each backplane input stream can have its own delay
offset value by programming the input delay offset
registers (DOS0 to DOS5). Possible adjustment can
range up to +4 master clock (C16i) periods forward
with resolution of half master clock period. See Table
10 and Table 11, and Figure 9, for frame input delay
offset programming.
Output Advance Offset Selection
The MT90863 allows users to advance individual
backplane output streams which operate at 8.192Mb/
s (STio0-23) by half a master clock (C16i) cycle. This
feature is useful in compensating for variable output
delays caused by various output loading conditions.
The frame output offset registers (FOR0 & FOR1)
control the output offset delays for each backplane
output stream via the OFn bit programming. Table 12
and Figure 10 detail frame output offset
programming.
Serial Input Frame Alignment Evaluation
The MT90863 provides the frame evaluation inputs,
FEi0 to FEi23, to determine different data input
delays with respect to the frame pulse F0i. By using
the frame evaluation input select bits (FE0 to FE4) of
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