MT90870 Zarlink Semiconductor, Inc., MT90870 Datasheet - Page 10

• Manufacturer Part Number: MT90870
• Description: Flexible 12k Digital Switch (F12kDX)
• Manufacturer: Zarlink Semiconductor, Inc.

MT90870
Preliminary Information
1.0
Bidirectional and Unidirectional Applications
The MT90870 has a maximum capacity of 12,288 input channels and 12,288 output channels. This is
calculated from the maximum number of streams and channels: 48 input streams (32 Backplane, 16 Local) at
16.384Mb/s and 48 output streams (32 Backplane, 16 Local) at 16.384Mb/s.
One typical mode of operation is to separate the Backplane and Local sides, as shown in Figure 3 below.
BSTi0-31
LSTo0-15
32 streams
16 streams
BACKPLANE
LOCAL
BSTo0-31
LSTi0-15
32 streams
16 streams
MT90870
Figure 3 - 8,192 x 4,096 Channels (16Mb/s), Bidirectional Switching
In this system setup, the chip has a capacity of 8,192 input channels and 8,192 output channels on the
Backplane side as well as 4,096 input channels and 4,096 output channels on the Local side. Note that some
of the output channels on one side can come from the other side, ie: Backplane input to Local output switching.
Often a system design does not need to differentiate between Backplane and Local side, and merely needs
maximum switching capacity. In this case, the MT90870 can be used as shown in Figure 4 to give the full
12,288 x 12,288 channel capacity.
BSTi0-31
BSTo0-31
32 streams
32 streams
INPUT
OUTPUT
LSTi0-15
LSTo0-15
16 streams
16 streams
MT90870
Figure 4 - 12,288 x 12,288 Channels (16Mb/s), Unidirectional Switching
In this system, the Backplane and Local inputs and outputs are combined and the switch appears as a 48
stream input by 48 stream output switch. This style of operation is similar to older switch designs, such as the
MT90826.
Note, in either configuration the Backplane may be operated in the 32Mb/s Mode, providing 512 channels on
each of the 16 available input and output streams ( BSTi0-15 and BSTo0-15) operating at a data-rate of
32.768Mb/s, in conjunction with the Local streams (LSTi0-15 and LSTo0-15) operated at 16.384Mb/s. This
allows data-rate conversion between 32.768Mb/s and 16.384Mb/s without loss to the switching capacity.
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