mt90868ag2 Zarlink Semiconductor, mt90868ag2 Datasheet - Page 24

• Manufacturer Part Number: mt90868ag2
• Description: 32,768 X 8,192 Channels High Bandwidth Digital Switch With Up To 128 Streams On Backplane And 128 Streams On Local And Data Rates From 8 To 32 Mbps
• Manufacturer: Zarlink Semiconductor

3.0
The MT90868 provides users with four switching paths, namely "backplane-to-local", "local-to-backplane",
"backplane-to-backplane" and "local-to-local". The switching configuration is controlled by programming the local
connection and the backplane connection memories.
The "backplane-to-local" switching path allows the device to perform data switching between the backplane input
port and the local output port among 32,768 backplane input channels and 8,192 local output channels. The local
connection memory determines the switching configurations. See Table 30 and Table 31 for the details.
The "local-to-backplane" switching path allows users to perform data switching between the local input port and the
backplane output port among 8,192 local input channels and 16,380 or 32,760 backplane output channels when
operated in the 16Mb/s or 32Mb/s mode respectively. The last channel (Ch255 or Ch511) of the backplane output
streams BSTo60 to BSTo63 or BSTo58 to BSTo63 contains invalid output data for the 16Mb/s or 32Mb/s mode
respectively. Avoid using the last channel of these streams for the "local-to-backplane" data switching. The
backplane connection memory determines the switching configurations. See Table 32 for the details.
The "local-to-local" switching path allows users to perform data switching between the local input and the local
output ports among 8,192 local input and 8,192 local output ports. The local connection memory determines the
switching configurations. See Table 30 and Table 31 for the details.
The "backplane-to-backplane" switching path allows users to perform data switching between the backplane input
and the backplane output ports. In this switching mode, only two backplane input streams can be selected by the
backplane data input selection register (BDISR). The switching capacity is 512 x 512 or 1,024 x 1,024 backplane
channels for the 16Mb/s or 32Mb/s mode respectively. The BDISR register selects two backplane input data
streams, namely, Stream A and Stream B to support the "backplane-to-backplane" switching. The backplane
connection memory determines the switching configurations. See Table 33 for the details.
3.1
The usage of the local input channel delay buffer and the local output channel advancement buffer affects the data
throughput delay for the four data switching paths. The usage of these two buffers is controlled by the LICDEN and
the LOCAEN bits in the control register (CR). When LICDEN and LOCAEN bits are low, the "backplane-to-local"
switching path has a throughput delay of one frame plus 2 channel slots; the "local-to-backplane", the "backplane-
to-backplane" and the "local-to-local" switching paths have the throughput delay of two frames.
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Local-to-Backplane
Local-to-Local
Backplane-to-Local
Backplane-to-backplane
** Note: Input Buffer = Local input channel delay buffer
Switching Path
Output Buffer = Local output channel advancement buffer.
Table 2 - Data Delay Through the Device via Different Switching Paths
Switching Paths
Throughput Delay
1 Frame + 2 Ch
Input Buffer** OFF
Output Buffer**
(LOCAEN = 0)
(LICDEN = 0)
2 Frames
2 Frames
2 Frames
OFF
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1 Frame + 2 Ch
Output Buffer OFF
Input Buffer ON
(LOCAEN = 0)
(LICDEN = 1)
3 Frames
3 Frames
2 Frames
Data Delay
2 Frames + 2 Ch
Output Buffer ON
Input Buffer OFF
(LOCAEN = 1)
(LICDEN = 0)
2 Frames
3 Frames
2 Frames
2 Frames + 2 Ch
Output Buffer ON
Input Buffer ON
(LOCAEN = 1)
(LICDEN = 1)
3 Frames
4 Frames
2 Frames
Data Sheet