RELEASED
PM7350 S/UNI-DUPLEX
DATA SHEET
PMC-1980581
ISSUE 5
DUAL SERIAL LINK PHY MULTIPLEXER
9.3 High-Speed Serial Interface
The S/UNI-DUPLEX provides backplane interconnection via 100 to 200 Mb/s
serial links. All data destined to and coming from the core cell processing card
are concentrated on these high-speed links. The transceivers support UTP-5
cable lengths up to 10m. To avoid clock skew issues, no clock is transmitted and
the receivers recover a local clock from the incoming data.
Two bi-directional LVDS links are provided for redundancy; each link is intended
to be routed to different core cards. Both LVDS transmitters carry identical traffic
except for internally generated overhead. Both links are frequency locked to the
single input reference clock although their phase is not guaranteed to match. At
the LVDS receivers clock recovery and cell delineation are always active for both
receivers to allow a quick switch to the redundant core card with minimal cell
loss.
The serial links carry ATM cells with prepended bytes. The cell format is
illustrated in Fig. 9 and discussed in Section 12.2). The S/UNI-DUPLEX
appends the first four bytes and the Header Check Sequence (HCS) byte in the
upstream direction and strips them off and parses them in the downstream
direction. The remainder of the bytes in the data structure are transferred
transparently. The bytes are serialized most significant bit first. The bit stream is
a simple concatenation of the extended cells. Cell rate decoupling is
accomplished through introduction of stuff cells.
The transmitter inserts a correct CRC-8 that protects both the ATM cell header
and prepended bytes in the HCS byte. Cells with an errored HCS are counted
and then discarded. The receiver also uses the HCS byte for determining cell
delineation. Failure to establish cell alignment results in a loss of cell delineation
(LCD) alarm. The entire bit stream is scrambled with a x43 + 1 self-synchronous
scrambler.Table 16 summarizes the contents of the system prepended bytes.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
61
PMC [ PMC-SIERRA, INC ]
