PM7347 datasheet(64/341 Pages) PMC

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S/UNI®-JET Data Sheet

Released

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use

Document ID: PMC-1990267, Issue 3

When in frame, the SPLR extracts the path overhead octets and outputs them bit serially on

output RPOH, along with the RPOHCLK and RPOHFP outputs. Framing octet errors and path

overhead identifier octet errors are indicated as frame errors. Bit interleaved parity errors and

FEBEs are indicated. The yellow signal bit is extracted and accumulated to indicate yellow

alarms. Yellow alarms are declared when 10 consecutive yellow signal bits are set to logic one. It

is removed when 10 consecutive received yellow signal bits are set to logic zero. The C1 octet is

examined to maintain nibble alignment with the incoming transmission system sublayer bit

stream.

10.8

ATMF ATM Cell Delineator

The ATM Cell Delineator (ATMF) Block integrates circuitry to support HCS-based cell

delineation for non-PLCP based transmission formats. The ATMF block accepts a bit serial cell

stream from an upstream transmission system sublayer entity (such as the T3-FRMR, E3-FRMR,

or J2-FRMR Block) and performs cell delineation to locate the cell boundaries. For PLCP

applications, ATM cell positions are fixed relative to the PLCP frame, but the ATMF still

performs cell delineation to locate the cell boundaries.

Cell delineation is the process of framing to ATM cell boundaries using the HCS field found in

the ATM cell header. The HCS is a CRC-8 calculation over the first four octets of the ATM cell

header. When performing delineation, correct HCS calculations are assumed to indicate cell

boundaries.

The ATMF performs a sequential bit-by-bit, a nibble-by-nibble (DS-3 direct mapped), or a byte-

by-byte (J2 and E3 direct-mapped) hunt for a correct HCS sequence. This state is referred to as

the HUNT state. When receiving a bit serial cell stream from an upstream transmission-system

sublayer entity, the bit, nibble, or byte boundaries are determined from the location of the

overhead.

When a correct HCS is found, the ATMF locks on the particular cell boundary and assumes the

PRESYNC state. This state verifies that the previously detected HCS pattern was not a false

indication. If the HCS pattern was a false indication then an incorrect HCS should be received

within the next DELTA cells. At that point a transition back to the HUNT state is executed. If an

incorrect HCS is not found in this PRESYNC period then a transition to the SYNC state is made.

In this state synchronization is not relinquished until ALPHA consecutive incorrect HCS patterns

are found. In such an event a transition is made back to the HUNT state. The state diagram of the

cell delineation process is shown in Figure 6.

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