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Lattice Semiconductor
ORCA ORSO42G5 and ORSO82G5 Data Sheet
49
Cell Mode Detailed Description
A common application for the ORSO42G5 and ORSO82G5 is to provide a bridge between a port card and a cell-
based switch fabric. In cell mode, the data in the Synchronous Payload Envelope (SPE) of the SONET frames is
further formatted into xed-length cells by the ORSO42G5 and ORSO82G5. The cell contents will typically be
unique to specic port card and switch devices. The ORSO42G5 and ORSO82G5 supports this application with a
“cell mode” of operation
The basic data ows in cell mode are shown in
Figure 35. Data to be transmitted is received from the FPGA logic
(see
Table 11 and
Table 12 for details of the core/FPGA signal assignments in the transmit direction which differ
signicantly from the SERDES only and SONET modes), inserted into the SPE of the SONET frame, scrambled
and transmitted from the SERDES block. In cell mode, multiple SERDES links are used to achieve desired band-
width. A two-link mode is supported in the ORSO42G5 and both two-link and eight-link cell modes are supported.
For such interfaces, data are cell-striped in a round-robin fashion across multiple links by the transmitter.
Figure 35. Basic Data Flows - Cell Mode
In the receive direction, the framed data are received from the SERDES block, descrambled and are passed into a
cell extractor which extracts individual cells from the payload portion of the SONET frame. The cells are then
passed through a FIFO that performs lane-to-lane deskew and a clock domain transfer. The clock domain transfer
is handled automatically using idle cell insertion and deletion.
The cells are passed into either the eight-link Input Port Controller IPC8 block (ORSO82G5 only) or to one of the
two-link IPC2 block(s), which reassemble the cells back into a single cell stream (destriping) which is sent to the
FPGA logic. (See
Table 13 and
Table 14 for details of the core/FPGA signal assignments in the receive direction.
As with the transmit path, the cell mode assignments differ signicantly from those for the SERDES only and
SONET modes).
SERDES and SONET processing has been described in previous sections and only features unique to the cell
mode will be discussed in the following sections. The cell format will be discussed rst, followed by a description of
the transmit path, which will include either a two-link or an eight-link Output Port Controller (OPC) block, and a
description of the receive path, including the two-link or eight-link Input Port Controller (IPC) blocks.
Cell Formats
Cells are arranged within a SONET (STS-48c) frame as shown in
Figure 36. A SONET STS-48c frame has 4176
(87 x 48) columns of SPE and 9 rows that gives a total of 37,584 bytes. In this implementation, data in a SPE is lim-
ited to xed size cells. Though four cell sizes are supported, only one cell size can be used at a time.
User
I/O
Receive (RX) Path
Transmit (TX) Path
Configurable
as
four
or
eight
data
channels
organized
in
two
blocks
MUX/DEMUX
&
SERDES
ORCA 4E04
FPGA Logic
Configurable
Cell
Processing
Pseudo-
SONET
Processing
MUX/DEMUX
and
SERDES