
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
122
10.6.1.1
SBI
Within the SBI Interface, the links are identified by the SPE and the tributary
number within the SPE.
At the per-link FIFOs, the SPE and Tributary number are mapped to a contiguous
space identified as physical links 0 through 83. These are referred to as the
physical link IDs. SPE1, Tributaries 1 to 28 are mapped to physical links 0-27.
SPE2, Tributaries 1 to 28 are mapped to physical links 28 to 55; and SPE3,
Tributaries 1 to 28 are mapped to physical links 56 to 83. If the SPEs are in E1
mode, then only the lowest 21 of the 28 possible tributaries are used.
If the SPEs are in DS3 mode, only one link per SPE is mapped. In this case,
only physical link IDs 0, 28, and 56 are used.
10.6.1.2
Clock/Data
Within the Clock and Data Interface, the external signals RSCLK/TSCLK and
RSDATA/TSDATA are identified by sequential numbers from 0 to 31.
Within the RCAS/TCAS, these 32 external signals are mapped to a contiguous
space identified as Virtual Links 0 through 83. To support multiple fractional TC
flows on a single external signal, RCAS/TCAS mapping is used to split a single
channelized external signal into multiple Virtual Links. At the per-link FIFOs, the
RCAS/TCAS Virtual Link naming convention is replaced 1:1 with the Physical
Link naming convention.
10.6.1.3
IMA
Within the IMA sublayer, mapping is performed between the physical link Ids and
the Any-PHY/UTOPIA L2 virtual PHY address. This mapping can be a one-to-one
relationship as for TC connections or it may be a many-to-one relationship as for
an IMA group.
The physical link to Virtual PHY mapping is independent in the RX and TX
directions.
The selection of the RX VPHY ID in Any-PHY or single port UTOPIA L2 mode is
unconstrained as this ID exists only as a prepend. In multiple port UTOPIA L2
mode, the RX VPHY ID must be a unique value between 0 and 30 for each flow.
The selection of the TX VPHY ID is limited by the following rule: