MT92220BG Zarlink Semiconductor, MT92220BG Datasheet - Page 59

• Manufacturer Part Number: MT92220BG
• Description: Description = 1023 Channel Voice Over IP/AAL2 Processor ;; Package Type = Epbga ;; No. Of Pins = 608
• Manufacturer: Zarlink Semiconductor

Data Sheet
MT92220
synchronization source. In this example, the look-up will be performed using only the Destination IP address and
Destination UDP port; which associates with profile #11, the other fields will be masked out.
The entire 320-bit masked identification key is then passed through a series of CRC calculations that produce a
56-bit result. These CRC calculations consist of a CRC-32, a CRC-16 and a CRC-8. In addition, before passing the
identification key through the CRC calculations, a 32-bit value can be added to each dword. This will allow conflict
resolution if the binary tree starts getting clogged with too many conflicting nodes: adding a 32-bit value scrambles
all the CRC to new random values and old conflicts will likely not reappear. Finally, the 4-bit profile value is annexed
to the CRC to produce a 60-bit identification key.
This 60-bit result is then used as the new identification key for the binary tree procedure. The binary tree can have
up to 128K nodes, distributed in any way. The system finds the node in the binary tree whose key is the same as
the one being searched for: it may also find no matching node. Once the binary tree search is complete, the
matching node's post-search confirmation structure is looked-up: it is checked to see if the headers of the
looked-up packet match those in the confirmation structure, validating the node as being the correct search node.
In this case, it can be assumed that there was a node in the binary tree that matched the packet, it matched in the
corresponding post-search structure (there cannot be more than one match per packet in the post-search
structures: this would be a fatal configuration error and would be flagged to a status bit in registers).
The format of the post-search confirmation structure is indicated in the next figure.
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