XRT74L73 Datasheet, PDF (152/488 Pages) Exar Corporation – 3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
PRELIMINARY
FIGURE 32. AN APPROACH TO PROCESSING SEGMENT OAM CELLS, VIA THE RECEIVE CELL PROCESSOR.
Receive Cell Processor
Cell
Delineation
HEC
Verification
User Cell Filter
Receive Utopia Block
Rx FIFO
Utopia
Interface
Path of OAM Cell
OAM Cell Buffer
Located at Address
(161h - 1A1h) in on-
Chip RAM.
OAM Cell is not “passed
through” to the Rx FIFO in
the Receive Utopia Block
3.3.2.4.2End-to-End Type OAM Cells
“End-to-End” type OAM cells, as the name implies, are
intended for something more than a point-to-point trans-
mission. In other words, an end-to-end type OAM cell
will be created at a source node, transmitted across a
single link, to a destination node. However, in this
case, the “end-to-end” OAM cell is not terminated at
this destination node; but is rather transmitted across
other links to other nodes within the network.
How the Receive Cell Processor Handles End-to-End
type OAM Cells
If the Receive Cell Processor determines that the in-
coming OAM Cell is an “End-to-End” type then it will
be written into the RxFIFO, within the Receive UTOPIA
Interface block. This act will allow the ATM Layer
processor to read in this OAM cell, from the UNI and
propagate this cell to other nodes in the network.
Note: The Receive Cell Processor will write the “End-to-
End” OAM cell to the RxFIFO, independent of the User Cell
Filter settings.
The Receive Cell Processor can also be configured to
write the contents of the “End-to-End” OAM celli into
the Receive OAM Cell Buffer. For details on how this
can be done, please see Section 7.3.2.4.1.
Figure 33 presents an illustration which depicts how
the Receive Cell Processor handles incoming End-to-
End type OAM Cells, if a “1” has been written to bit 3
(OAM Check Bit) of the “RxCP Configuration” regis-
ter.
FIGURE 33. APPROACH TO PROCESSING “END-TO-END” OAM CELLS
Receive Cell Processor
Cell
Delineation
HEC
Verification
User Cell Filter
Receive Utopia Interface Block
Rx FIFO
Utopia
Interface
The Contents of
the OAM Cell are
also written into
the “Receive OAM
Cell” buffer
Receive OAM Cell Buffer
Located at Address
(161h - 1A1h) in on-
Chip RAM.
“End-to-End” Type OAM
Cell is “passed through” to
the Rx FIFO in the Receive
Utopia Interface Block
Monitoring the Number of User/OAM Cells
To monitor the number of Valid cells (User and OAM)
that have been received by the Receive Cell Proces-
sor, read the PMON Received Valid Cell Count Reg-
isters (Address = 34h, and 35h). The bit-format of
these registers are presented below.
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