MT90528AG ZARLINK [Zarlink Semiconductor Inc], MT90528AG Datasheet - Page 110

• Manufacturer Part Number: MT90528AG
• Description: 28-Port Primary Rate Circuit Emulation AAL1 SAR
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

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Figure 45 shows an example external memory allocation for the structures listed above. The example assumes the
maximum memory allocation for each of the structures. The size and location of the structures are programmable
and do not necessarily have to be located at the addresses given in the example. The base address in the figure is
the base address of external memory.
Figure 46 shows another sample external memory allocation for the structures listed above. The example assumes
the minimum memory allocation for each of the structures. The example assumes that no data cell transmission or
reception is required, that all channels are transmitted in trunking VCs carrying 128 channels (therefore requiring
only 7 VCs), and that minimum-sized Reassembly Circular Buffers are required. The size and location of the
structures are programmable and do not necessarily have to be located at the addresses given in the example. The
base address in the figure is the base address of external memory.
Data TX_SAR Cell Buffer
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Data RX_SAR Cell Buffer
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SDT Segmentation Circular Buffers
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SDT Reassembly Circular Buffers
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Circular Buffer Size > Maximum Lead + Number of Bytes per Channel per Cell
possible sizes: 16 cells, 32 cells, 64 cells, 128 cells (each cell occupies 64 bytes; 32 words)
maximum of 4 K words
possible sizes: 16 cells, 32 cells, 64 cells, 128 cells (each cell occupies 64 bytes; 32 words)
maximum of 4 K words
each channel to be transmitted in ATM cells requires its own Segmentation Circular Buffer. Each buffer
occupies 64 words
up to 896 channels (28 ports x 32 channels per port) can be transmitted
maximum of 56 K words
each channel which will be receiving data from ATM cells requires its own Reassembly Circular Buffer.
Each buffer has a programmable size, on a per-VC basis.
the size selected for a Reassembly Circular Buffer should be based upon the amount of CDV expected
on the VC, as well as the number of channels being carried on the VC (more buffering is required on a
per-channel basis for VCs with fewer channels, because more data for each channel is received at once
upon cell reception). Note that CDV can be accounted for within a larger-than-necessary buffer by
programming the Maximum Lead value.
programmable sizes for Reassembly Circular Buffers are as follows: 64 words, 128 words, 256 words,
512 words, and 1024 words
up to 896 channels (28 ports x 32 channels per port) can be received
maximum of 896 K words
Maximum Lead = 2 bytes + ((2*CDV) / (0.125 ms/byte)). CDV is in ms.
Number of Bytes per Channel per Cell = roundup(N/47). N = # of channels per VC.
Zarlink Semiconductor Inc.
MT90528
110
Data Sheet