PM5366-PI datasheet(122/267 Pages) PMC

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PRELIMINARY

PM5366 TEMAP-84

DATASHEET

PMC-2010672

ISSUE 1

HIGH DENSITY 84/63 CHANNEL VT/TU MAPPER

AND M13 MULTIPLEXER

PROPRIETARY AND CONFIDENTIAL

110

channel bits. Fixed stuff bytes are used to fill the remaining bytes. Please refer

to section 9.27 for a description of the DS3 mapping.

9.32.1 DS3 Mapper Serializer

High speed serial data from the DS3-TRAN block is deserialized and written into

the Elastic Store.

9.32.2 DS3 Mapper Elastic Store

The elastic store block is provided to compensate for frequency differences

between the DS3 stream from the DS3-TRAN block and the STS-1 (STM-0/AU3)

SPE capacity. The DS3 Serializer writes data into the elastic store at the

TICLK/8 rate while data is read out at the stuffed STS-1 (STM-0/AU3) byte rate.

If an overflow or underflow condition occurs, an interrupt is optionally asserted

and the Elastic Store read and write address are reset to the startup values

(logically 180 degrees apart).

The Elastic store is 128 bits (16 bytes) to allow for a fixed read/write pointer lag

of 7 bytes (3 bytes for TOH, 1 byte for POH, 2 bytes for R bits, and 3 overhead

bits which is rounded-up to 1 byte). Four bytes are also added on either side for

positive and negative threshold detection.

9.32.3 DS3 Synchronizer

The DS3 Synchronizer performs the mapping of the DS3 into the STS-1

(STM-0/AU3) SPE. The DS3 Synchronizer monitors the Elastic Store level to

control the stuffing algorithm to avoid overflow (i.e. run faster) and underflow

(i.e. run slower) conditions. The fill level of the elastic store is monitored and

stuff opportunities in the DS3 mapping are used to center the Elastic Store. To

consume a stuff opportunity, the five C-bits on a row are set to ones and the S bit

is used to carry an DS3 information bit. When the S bit is not used to carry

information, the C-bits on the row are set to zeros.

The DS3 synchronizer uses a fixed bit leaking algorithm which leaks 8 bits of

phase buildup in 500 µs. The 8 kHz STS-1 (STM-0/AU3) frame interval is

subdivided into 9 rows. Each row contains one stuff opportunity. Table 8

illustrates the stuffing implementation where S means stuff bit and I means an

information bit (DS3 data).

PM5366-PI Datasheet(PDF) 122 Page - PMC-Sierra, Inc