PMC-Sierra, Inc.
PRELIMINARY
PM5381 S/UNI-2488
DATASHEET
PMC-2000489
ISSUE 1
SATURN USER NETWORK INTERFACE FOR 2488 MBIT/S
opportunity byte. Data is read out of the FIFO in the Elastic Store block at the outgoing byte rate
by the Pointer Generator. Analogously, outgoing pointer justifications are accommodated by
reading from the FIFO during the negative stuff opportunity byte or by not reading during the
positive stuff opportunity byte.
The FIFO read and write addresses are monitored. Pointer justification requests will be made to
the Pointer Generator based on the proximity of the addresses relative to programmable
thresholds. The Pointer Generator schedules a pointer increment event if the FIFO depth is
below the lower threshold and a pointer decrement event if the depth is above the upper
threshold. FIFO underflow and overflow events are detected and path AIS is optionally inserted
in the outgoing data stream for three frames to alert downstream elements of data corruption.
10.6.2 Pointer Generator
The Pointer Generator generates the H1 and H2 bytes in order to identify the location of the path
overhead byte (J1) and all the synchronous payload envelope bytes (SPE) of the STS-48c
(VC16-16c) payloads. Within the pointer generator algorithm, five states are defined as shown
below:
NORM_state (NORM)
AIS_state (AIS)
NDF_state (NDF)
INC_state (INC)
DEC_state (DEC)
The transition from the NORM to the INC, DEC, and NDF states are initiated by events in the
Elastic Store block. The transition to/from the AIS state are controlled by the pointer interpreter
in the Receive High Order Path Processor block. The transitions from INC, DEC, and NDF states
to the NORM state occur autonomously with the generation of special pointer patterns.
Proprietary and Confidentail to PMC-Sierra Inc., and for its Customer’s Internal Use
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PMC [ PMC-SIERRA, INC ]
