PM5347 datasheet(73/302 Pages) PMC

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PM5347 S/UNI-PLUS

DATA SHEET

PMC-941033

ISSUE 6

SATURN USER NETWORK INTERFACE PLUS

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

and corrected while the HCS Verification state machine is in the 'Correction

Mode' state. The second counter accumulates uncorrectable HCS errors which

are HCS bit errors detected while the HCS Verification state machine is in the

'Detection Mode' state or HCS bit errors detected but not corrected while the

state machine is in the 'Correction Mode' state. The 21-bit receive cell counter

counts all cells written into the receive FIFO. Filtered cells are not counted.

Each counter may be read through the microprocessor interface. Circuitry is

provided to latch these counters so that their values can be read while

simultaneously resetting the internal counters to 0 or 1, if appropriate, so that a

new period of accumulation can begin without loss of any events. It is intended

that the counter be polled at least once per second so as not to miss HCS error

events.

GFC Extraction Port

The GFC Extraction Port outputs the received GFC bits in a serial stream. The

four GFC bits are presented for each received cell, with the RCP output

indicating the position of the most significant bit. The updating of RGFC by

particular GFC bits may be disabled through an internal register. The serial link

is forced low if cell delineation is lost.

Receive FIFO

The Receive FIFO provides FIFO management and the asynchronous interface

between the S/UNI-PLUS device and the external environment. The receive FIFO

can accommodate four cells. The receive FIFO provides for the separation of the

STS-3c/1 (STM-1) line or physical layer timing from the ATM layer timing.

The FIFO supports two data structures. The first data structure consists of

twenty-seven 16-bit words comprising the five octet cell header, a cell header

status octet and the forty-eight octet payload. The second data structure

consists of fifty three 8-bit words comprising the five octet cell header and the

forty-eight octet payload. Refer to the Operation section for more detail on these

data structures.

Management functions include filling the receive FIFO, indicating when cells are

available to be read from the receive FIFO, maintaining the receive FIFO read

and write pointers, and detecting FIFO overrun and underrun conditions. Upon

detection of an overrun, the FIFO is automatically reset. Up to four cells may be

lost during the FIFO reset operation. Upon detection of an underrun, the

offending read is ignored. FIFO overruns are indicated through a maskable

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