PM7340 S/UNI-IMA-8
PRELIMINARY
INVERSE MULTIPLEXING OVER ATM
DATA SHEET
PMC-2001723
ISSUE 3
INVERSE MULTIPLEXING OVER ATM
payload is performed. The cell stream is then mapped into a T1 or E1 payload
with zeros inserted for the framing and overhead bits or bytes. If using an
unchannelized clock and data interface, the data is not mapped into the T1/E1
payload but instead is transmitted one bit for each provided clock pulse.
The links are then transmitted via the serial interfaces. The clock is provided from
each serial clock pin. An optional common-clock mode is provided to enable all
links to run from the same clock. If using an unchannelized clock and data
interface, the data is received one bit for each provided clock pulse.
On the receive side, data is received from the clock/data interface. The timeslots
are mapped to logical channels called links. The TC layer searches for cell
delineation as per the procedures outlined in ITU-T Recommendation I.432.1.
Once cell delineation is obtained, the payload is optionally descrambled and the
cells are passed to the IMA sub-layer. The TC layer provides counts of errored
headers as well as OCD and LCD error interrupts.
The receive IMA sublayer performs IMA-frame delineation and stuff-cell removal.
Based upon the ICP cell information, the S/UNI-IMA-8 determines the differential
delay between the links within a group and applies the link and group state
machine logic to coordinate the activation and deactivation of groups and links
with the far end. As cells are received, they are stored in an external FIFO
structure. This structure is based upon the IMA frame boundaries and the IMA
frame sequence number. When links or groups are determined to be active by
the link and group state machines, the data is played out to the Any-
PHY/UTOPIA interface at a constant rate to mimic the existence of a single
higher bandwidth physical link.
Once a group of links is established, links can be dynamically added or deleted
from the group. Under management control, the S/UNI-IMA-8 will perform all
necessary steps to add or delete links from previously established groups.
In order to aid with diagnostics, a line side loopback and a UTOPIA side loopback
are provided. Also, an ICP cell trace feature is provided. When the ICP cell trace
has been enabled for a group, the S/UNI-IMA-8 will place those ICP cells where
a SCCI field change is detected into a buffer that is accessible to the
microprocessor.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
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PMC [ PMC-SIERRA, INC ]
