RELEASED
PM73123 AAL1GATOR-8
DATASHEET
PMC-2000097
ISSUE 2
8 LINK CES/DBCES AAL1 SAR
the SYNC state when underrun occurs, when the next cell arrives, potentially
some time later, the state machine will still be in the SYNC state.
9.2.2.2.5 Line Data Storage
The RALP reads the ATM cell from the RALP_FIFO, verifies the header, and
determines the queue to which the cell belongs. It then locates the data bytes of
the cell and writes them into frame buffers provided for that line. Receive queues
exist in the external memory, and each line is allocated 16 kBytes of memory.
This provides for 32 multiframes of E1 data (16 multiframes if T1 signaling is
used) or 16 multiframes of T1. The queues are used in a wrap-around fashion.
Read and write pointers are used at the frame and multiframe level to access the
receive queue.
Figure 37 on page 116 shows cell reception. Read and write pointers are used at
the frame and multiframe level to access the correct data byte location. The
RALP writes sequential cell data bytes into successive DS0 locations assigned to
that queue.
When the RALP encounters signaling bytes, it places them in the receive
signaling buffer. The buffers are organized in a multiframe format. There is one
signaling nibble per multiframe allocated to each DS0 channel. Therefore, 32
bytes of signaling storage are allocated for each multiframe worth of data buffer.
The signalling bytes are not used for UDFmodes.
Figure 37 and the figures that follow illustrate these points and identify how
different data formats are stored in the data and signaling buffers.
PMC-SIERRA, INC. PROPRIETARY AND CONFIDENTIAL
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