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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

Table 5 C1 Octet Pattern

Stuff Length

C1(Hex)

The SPLT block generates a stuff length pattern of 18, 19, or 20 octets determined by the phase

alignment of the start of the G.751 E3 frame and the start of the E3 PLCP frame. The REF8KI

input is provisioned to loop time the PLCP transmit frame to an externally applied 8 kHz

reference.

The Zn, growth octets are set to 00H. The Zn octets may be inserted from an external device via

the path overhead stream input, TPOH.

10.19 TXCP-50 Transmit Cell Processor

The Transmit Cell Processor (TXCP-50) Block integrates circuitry to support ATM cell payload

scrambling, header check sequence (HCS) generation, and idle/unassigned cell generation.

The TXCP-50 scrambles the cell payload field using the self synchronizing scrambler with

polynomial x43 + 1. The header portion of the cells may also be scrambled. Note: Cell payload

scrambling may be disabled in the S/UNI-JET, although it is required by ITU-T Recommendation

I.432. The ATM Forum DS3 UNI specification requires that cell payloads are scrambled for the

DS3 physical layer interface. However, to ensure backwards compatibility with older equipment,

the payload scrambling may be disabled.

The HCS is generated using the polynomial, x8 + x2 + x + 1. The coset polynomial x6 + x4 + x2 +

1 is added (modulo 2) to the calculated HCS octet as required by the ATM Forum UNI

specification, and ITU-T Recommendation I.432. The resultant octet optionally overwrites the

HCS octet in the transmit cell. When the transmit FIFO is empty, the TXCP-50 inserts

idle/unassigned cells. The idle/unassigned cell header is fully programmable using five internal

registers. Similarly, the 48-octet information field is programmed with an 8-bit repeating pattern

using an internal register.

10.20 TXFF Transmit FIFO

The Transmit FIFO (TXFF) provides FIFO management and the S/UNI-JET transmit cell

interface. The transmit FIFO contains four cells. The FIFO depth may be programmed to four,

three, two, or one cells. The FIFO provides the cell rate decoupling function between the

transmission system physical layer and the ATM layer.

The general management functions of the TXFF include:

• Emptying cells from the transmit FIFO.

• Indicating when the transmit FIFO is full.

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