MT90502_06 ZARLINK [Zarlink Semiconductor Inc], MT90502_06 Datasheet - Page 72

• Manufacturer Part Number: MT90502_06
• Description: Multi-Channel AAL2 SAR
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

Data received on all three ports is examined for parity errors and an interrupt is raised if an error is found. Cells are
not discarded if a parity error is detected. Register 60Ah indicates on which port the parity error is detected.
The ATM HEC is not examined on received cells.
2.6.5
Cells are read in a cyclic manner from the 4-cell input FIFOs. Cells from the TX_SAR that contain a '0' in the MSB
of the TXD field (see Figure 21, “TX Cell Format,” on page 50) are written into the output FIFOs designated by the
three LSBs of the TXD field. The TXD field may also indicate that the cell is routed through one of the 3 look-up
tables. Therefore, the cell follows the same path as if it came from one of the 3 UTOPIA input ports. Cells written
into the RX_SAR FIFO can be directed to the SAR portion (cells to be formatted into TDM streams), to the data cell
portion (to be examined by the CPU), or to both. This is indicated by the RXD field (see Figure 35, “RX Cell
Format,” on page 72) in cells written into the RX_SAR output FIFO.
2.6.5.1
Cells received on the UTOPIA port are designated as “known” or “unknown” based on the result of a mask & match
process (configured for each port). For a cell to be considered “known”, all VPI/VCI bits whose corresponding mask
bit is '1' must have the value contained in the corresponding bit of the match register. In addition, the MT90502 can
be configured to eliminate null cells (those with VPI = 0 and VCI = 0). For the purpose of null cell elimination, the
NNI/UNI can be included on a per-port basis (Register 60Eh).
Unknown cells can be discarded or directed to one or more output FIFOs. All unknown non-OAM cells from a port
are discarded or directed to the same location(s) and all unknown OAM cells from a port are discarded or directed
to the same location(s). Unknown cells can be directed differently for each port on which they were received.
Cell Routing
RX SAR Output FIFO structure is 64-bytes in size, located in internal memory at addresses 3000h to 3FFEh.
Port #:
VC Number:
RXD:
Mask & Match Process
+3C
+3A
+3E
+30
+32
+34 Port #
+36
+38
+0
+2
+4
+6
b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3
(of cells written in each of the internal input cell FIFOs in the UTOPIA interface)
“00” = comes from LUT A, “01” = comes from LUT B, “10” = comes from LUT C; others = reserved
indicates the VC to which this cell is destined, if it is destined to the RX SAR.
RX Destination. “1x” = Destined to RX SAR, “x1” = destined to AAL0 FIFO.
GFC/VPI
Payload Byte 44
Payload Byte 46
Payload Byte 0
Payload Byte 2
VCI [11:0]
RX Cell Format
Figure 35 - RX Cell Format
Zarlink Semiconductor Inc.
VPI
VC Number
MT90502
72
Payload Byte 45
Payload Byte 47
Payload Byte 1
Payload Byte 3
OAM
VCI [15:12]
b2
PTI
b1
RXD
CLP
b0
Reserved
Data Sheet