MT90225AG Zarlink Semiconductor, MT90225AG Datasheet - Page 25

• Manufacturer Part Number: MT90225AG
• Description: Description = 16 Port TC PHY For T1, E1 And DSL ;; Package Type = N/a ;; No. Of Pins =
• Manufacturer: Zarlink Semiconductor

Data Sheet
3.0 The ATM Receive Path
The receive path corresponds to the cell flow from the PHY (serial TDM) interfaces to the ATM UTOPIA Interface.
The MT90225/226 provides cell delineation and optional cell filtering to discard Unassigned or Idle cells on each link.
Up to sixteen/eight incoming serial (typically TDM) lines can be connected to the MT90225/226 receiver and
forwarded to the UTOPIA L2 interface served by an external ATM-Layer device. Figure 5 illustrates four of the
sixteen possible UTOPIA ports that can be addressed through the UTOPIA Interface.
The size of the RX UTOPIA FIFO is fixed at 4 cells. The Idle cells are automatically removed at the RX TDM block
and all other valid received cells are transferred to the RX UTOPIA FIFO.
3.1 Cell Delineation Function
This block provides the circuitry necessary to perform functions such as Cell Delineation (CD), cell payload
de-scrambling, HEC verification and filtering of Idle cells. The CD circuit delineates ATM cells received from the
payload of the T1, E1, J1 or DSL frame through the flexible TDM Interface.
When performing delineation, valid HEC calculations are interpreted to indicate cell boundaries. The CD circuit
performs a sequential hunt for a correct HEC sequence. While performing this hunt, the cell delineation state
machine is in the HUNT state. Figure 6 depicts a state diagram of the cell delineation operation.
Figure 5 - Example of TC Mode Operation (Using Four of Sixteen Possible UTOPIA-Output Ports)
RXCK
RXSYNC
DSTi
RXCK
RXSYNC
DSTi
RXCK
RXSYNC
DSTi
RXCK
RXSYNC
DSTi
S/P
S/P
S/P
S/P
Delineation
Delineation
Delineation
Delineation
Consecutive
Incorrect HEC
(cell by cell)
ALPHA
Cell
Cell
Cell
Cell
Figure 6 - Cell Delineation State Diagram
HUNT
System Clock
Zarlink Semiconductor Inc.
Valid HEC (byte by byte)
Removal
Removal
Removal
Removal
Idle Cell
Idle Cell
Idle Cell
Idle Cell
Incorrect HEC
(cell by cell)
SYNC
Rx UTOPIA FIFO
DELTA Consecutive
Correct HEC
(cell by cell)
PRESYNC
Interface
UTOPIA
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