MT90520AG ZARLINK [Zarlink Semiconductor Inc], MT90520AG Datasheet - Page 52

• Manufacturer Part Number: MT90520AG
• Description: 8-Port Primary Rate Circuit Emulation AAL1 SAR
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

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The filter considers the headers of cells received at the RX UTOPIA Interface; if cells pass through the Match and
Match Enable filters successfully, the “accepted” cells are written to the RX UTOPIA FIFO.
The operation of OAM & VPI/VCI filter sub-module can be summarized by the flow chart in Figure 16.
The header of the incoming cell is transferred from the RX UTOPIA Interface to the OAM & VPI/VCI filter. Once the
header has been received, the VPI and VCI fields are examined. If all the bits of the VPI field and all the bits of the
VCI field are equal to zero, the cell is a filler cell (i.e., a null cell), and it is discarded. Otherwise, the processing of
the cell continues in the Match and Match Enable filter.
cells whose VPI and/or VCI fall outside the Match and Match Enable filters which are configured via the
registers at byte addresses 4008h - 400Ch.
OAM cells (i.e., cells where the most significant bit of the PTI field in the cell header is set). OAM cells are
discarded if the user clears the GLOBAL_OAM_SEL bit in the UTOPIA Configuration Register at 4000h
Cell Discarded
NO
OAM_SEL = 1?
OAM cell?
GLOBAL_
YES
MATCH
Figure 16 - OAM & VPI/VCI Filter Flowchart
NO
YES
RX UTOPIA Interface
External PHY or ATM
Zarlink Semiconductor Inc.
Match Enable
Null Cell?
Match and
MT90520
Device
Filter
52
Incoming Cell
NO
32-cell internal RX
YES
NO MATCH
UTOPIA FIFO
Cell Discarded
Cell Discarded
Data Sheet