S/UNI®-ATLAS-3200 Telecom Standard Product Data Sheet
Preliminary
10.1.8 Packet-Bypass Mode
The S/UNI-ATLAS-3200 can operate in a mixed packet/cell environment. In this case, the PHY
interfaces must be configured as POS-PHY Level 3 interfaces. Each PHY queue can be
configured to be in packet mode by writing the Enable bit for that PHY in the Bypass Data Queue
to logic 1, and setting the corresponding bit to logic 0 in the Input and Output Data Queues. The
PHY queue can be configured to be in cell mode by writing the Enable bit for that PHY in the
Input and Output Data Queues to logic 1, and setting the corresponding bit to logic 0 in the
Bypass Data Queue; in all cases, PHYs in the Input and Output SDQs must be set to ATM Cell
mode (FIFO_TYPE = 0) and those in the Bypass SDQ to Packet mode (FIFO_TYPE = 1).
If a PHY is in packet mode, it is bypassed around the cell processor via the Bypass Data Queue.
Effectively, all packet traffic cuts through the S/UNI-ATLAS-3200 unchanged, except for the
PHY mapping function in the Link blocks.
Conversely, if a PHY is in cell mode, then its traffic is assumed to be ATM; hence the traffic is
subject to the normal cell processing functions including policing, FM and PM, as described in
the previous subsections.
POS-PHY Level 3 is capable of transferring both packets and cells. Using POS-PHY Level 3,
Cells are transferred as fixed-length packets. The format of the packet is configured in the same
way as for UTOPIA level 3, by specifying (in the interface blocks) the presence or lack of
prepended, postpended, or HEC/UDF words. Thus the length of the ATM-cell packets can be 52,
56, 60, or 64 bytes. Non-ATM packets, of course, can be of any length. If even one of the PHY
devices is configured to be in packet mode, then the S/UNI-ATLAS-3200 must use POS-PHY
signaling at both its input and output interfaces. On the other hand, if all the PHY devices are
configured to be in cell mode, then the S/UNI-ATLAS-3200 may use UTOPIA signaling or POS-
PHY signaling.
10.1.9 ATM Cell Format
Whether in POS-PHY or UTOPIA mode, the S/UNI-ATLAS-3200 can accept ATM cells with or
without HEC/UDF, and with one or two Prepended/Postpended d-words. The format of the cell
must be preprogrammed at each interface, but it may be different at the device output than at the
input. Total cell lengths of 52, 56, 60, or 64 bytes are supported, and the total number of
prepended + postpended d-words must be less than or equal to 2. The format of the extended
ATM cells is illustrated in Figure 9.
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-1990553, Issue 4
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PMC [ PMC-SIERRA, INC ]
