PMC-Sierra, Inc.
PM5356
S/UNI-622-MAX
DATASHEET
S/UNI-622-MAX
PMC-1980589
ISSUE 5
SATURN USER NETWORK INTERFACE (622-MAX)
Transmit FIFO
The Transmit FIFO is responsible for holding cell provided through the Transmit System Interface
until they are transmitted. The transmit FIFO can accommodate a maximum of 4 cells. The cells
are written in with a single 16 bit data bus running off TFCLK and are read out using the
SONET/SDH clock. Internal read and write pointers track the cells and indicate the fill status of
the Transmit FIFO. Separate read and write clock domains provide for separation of the physical
layer line timing from the System Link layer timing (TFCLK).
Idle/Unassigned Cell Generator
The Idle/Unassigned Cell Generator inserts idle or unassigned cells into the cell stream when
enabled. Registers are provided to program the GFC, PTI, and CLP fields of the idle cell header
and the idle cell payload. The idle cell HCS is automatically calculated and inserted.
Scrambler
The Scrambler scrambles the 48 octet information field. Scrambling is performed using a parallel
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implementation f the self-synchronous scrambler (x + 1 polynomial). The cell headers are
transmitted unscrambled, and the scrambler may optionally be disabled.
HCS Generator
The HCS Generator performs a CRC-8 calculation over the first four header octets. A parallel
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2
6
4
2
implementation of the polynomial, x +x +x+1, is used. The coset polynomial, x +x +x +1, is
added (modulo 2) to the residue. The HCS Generator optionally inserts the result into the fifth
octet of the header.
10.12 ATM UTOPIA System Interfaces
The S/UNI-622-MAX system interface is configured for ATM cell data. The system interface
provides either a UTOPIA level 2 compliant bus or a UTOPIA Level 3 compatible bus to allow the
transfer of ATM cells between the ATM layer device and the S/UNI-622-MAX.
10.12.1 Receive ATM Interface
The Receive ATM FIFO (RXCP) provides FIFO management at the S/UNI-622-MAX receive cell
interface. The receive FIFO contains four cells. The FIFO provides the cell rate decoupling
function between the transmission system physical layer and the ATM layer.
In general, the management functions include filling the receive FIFO, indicating when the receive
FIFO contains cells, maintaining the receive FIFO read and write pointers, and detecting FIFO
overrun and underrun conditions.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
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PMC [ PMC-SIERRA, INC ]
