PM7341 datasheet(117/413 Pages) PMC

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PRELIMINARY

INVERSE MULTIPLEXING OVER ATM

PM7341 S/UNI-IMA-84

DATASHEET

PMC-2000223

ISSUE 4

INVERSE MULTIPLEXING OVER ATM

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

119

a data byte belongs using only the outgoing link identity, as no time-slots are

associated with unchannelized links. The link clock is only active during bit-times

containing data to be transmitted; it is inactive during bit-times that are to be

ignored by the downstream devices, such as framing and overhead bits.

10.5.2 TX Null Framer (SDFR84)

Since data is carried over the SBI bus in a framed format, the ATM payload must

be mapped into the appropriate T1, E1, or DS3 format. The Null Framer creates

bit streams with the appropriate number of bits without performing the actual

framing bit generation or signaling insertion.

For T1, a T1 frame is created by adding a bit as a placeholder for the framing bit

and the ATM data is mapped into the 24 DS0 channels.

For E1, placeholders are inserted for channels 0 and 16, which are reserved for

signaling, and ATM data is mapped into the remaining 30 channels. (Channels 1

through 15 and 17 through 31).

For DS3, a bit is inserted every 21 nibbles for the frame/sub-frame bits.

10.5.3 Insert Scaleable Bandwidth Interconnect (INSBI)

The Insert Scaleable Bandwidth Interconnect block maps up to eighty-four

T1(1.544 Mbp)s links, sixty-three E1 (2.048 Mbps) links, or three DS3 (44.736

Mbps) links into the SBI bus. The 1.544 Mbps links are T1 framed (channelized)

with null framing bits. The 2.048 Mbps links are E1 framed (channelized) with null

framing bytes. The 44.736 Mbps links are also framed DS3 with null framing bits.

All links sourced from the S/UNI-IMA-84 over the SBI bus must be framed prior to

transmission.

Links inserted into the SBI bus are timed from the framer device (e.g. PM8315

TEMUX, PM8316 TEMUX-84). In other words, the INSBI always acts as a clock

slave. The INSBI performs SBI tributary justifications under command from the

AJUST_REQ signal..

10.5.4 Extract Scaleable Bandwidth Interconnect (EXSBI)

The Extract Scaleable Bandwidth Interconnect (EXSBI)block demaps up to 84 T1

(1.544 Mbps) links, 63 E1 (2.048 Mbps) links, or up to 3 DS3 (44.736 Mbps) links

from the SBI bus. The 1.544 Mbps links must be T1 framed and channelized. The

PM7341 Datasheet(PDF) 117 Page - PMC-Sierra, Inc