PM7340 S/UNI-IMA-8
PRELIMINARY
INVERSE MULTIPLEXING OVER ATM
DATA SHEET
PMC-2001723
ISSUE 3
INVERSE MULTIPLEXING OVER ATM
Read_delay
Reads a snapshot of the link-defect status and
link-delay information for all of the links within
the group. The delay information can be used to
determine differential delay, the link with the
most delay, and any other delay characteristics
of the group. The delay information is provided
in units of cells.
Adjust_delay
Adjusts the delay of a group by removing the
amount of specified delay. While the delay is
being adjusted, links cannot be added or
recovered for the group.
In addition to performing commands from the plane management, the RIPP
processes the ICP cells forwarded by the RDAT. When ICP cells arrive from a
group, they may be out of order in time due to differential delay between links.
The RIPP must examine the ICP cell and determine if it has any new information
that needs processing. This can be determined via the IMA frame number and
the SSCI field. When processing the ICP cells and the link states, attention must
be taken not to violate the group wide procedures. When link or group states are
changed, updated ICP cells are sent to the TIMA for transmission. Any state
changes are also communicated to the appropriate schedulers and round-robin
processors.
10.2.5.1
Group Start-up and Differential Delay
On group start-up, when at least Prx Links obtain IMA frame synchronization, the
links will be evaluated. As each link is evaluated, the differential delay of the
accepted links is tracked. If a link cannot be accepted because the acceptance of
the link would violate the programmed maximum DCB threshold (fastest link
minus current data read pointer), the link will remain in the unusable state and
begin to report a LODS defect. Accepted links will begin to report a usable state.
At this point, as additional links acquire frame sync, they are evaluated and either
are accepted or begin to report an LODS defect. When all links have acquired
frame sync or the timer has expired, the accepted receive links are reported as
active. If at least Prx links have been accepted, the group state machine
transitions to operational.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
74
PMC [ PMC-SIERRA, INC ]
