Device Overview
The MT90870 has two data ports, the Backplane and the Local port. The Backplane port has two modes of operation, either 32 input and 32 output streams operated at 2.048 Mb/s, 4.096 Mb/s, 8.192 Mb/s or 16.384 Mb/s, in any combination, or 16 input and 16 output streams operated at 32.768 Mb/s. The Local port has 16 input and 16 output streams operated at 2.048 Mb/s, 4.096 Mb/s, 8.192 Mb/s or 16.384 Mb/s, in any combination. The MT90870 contains two data memory blocks (Backplane and Local) to provide the following switching path configurations:

• Backplane-to-Local, supporting 8 K x 4 K data switching,
• Local-to-Backplane, supporting 4 K x 8 K data switching,
• Backplane-to-Backplane, supporting 8 K x 8 K data switching.
• Local-to-Local, supporting 4 K x 4 K data switching.

The device contains two connection memory blocks, one for the Backplane output and one for the Local output. Data to be output on the serial streams may come from either of the data memories (Connection Mode) or directly from the connection memory contents (Message Mode).

FEATUREs
• 12,288-channel x 12,288-channel non-blocking
   unidirectional switching.The Backplane and
   Local inputs and outputs can be combined to
   form a non-blocking switching matrix with 48
   stream inputs and 48 stream outputs
• 8,192-channel x 4,096-channel blocking
   Backplane to Local stream switch
• 4,096-channel x 8,192-channel non-blocking
   Local to Backplane stream switch
• 8,192-channel x 8,192-channel non-blocking
   Backplane input to Backplane output switch
• 4,096-channel x 4,096-channel non-blocking
   Local input to Local output stream switch
• Rate conversion on all data paths, Backplane to
   Local, Local to Backplane, Backplane to
   Backplane and Local to Local streams
• Backplane port accepts 32 ST-BUS streams with
   data rates of 2.048 Mb/s, 4.096 Mb/s, 8.192 Mb/s
   or 16.384 Mb/s in any combination, or a fixed
   allocation of 16 streams at 32.768 Mb/s
• Local port accepts 16 ST-BUS streams with data
   rates of 2.048 Mb/s, 4.096 Mb/s, 8.192 Mb/s or
   16.384 Mb/s, in any combination
• Per-stream channel and bit delay for Local input streams
• Per-stream channel and bit delay for Backplane input streams
• Per-stream advancement for Local output streams
• Per-stream advancement for Backplane output streams

APPLICATIONs
• Central Office Switches (Class 5)
• Mediation Switches
• Class-independent switches
• Access Concentrators
• Scalable TDM-Based Architectures
• Digital Loop Carriers