S/UNI-IMA-4 Telecom Standard Product Data Sheet
Released
Command
Read_event
Description
Read and clear the latched event status, and read the link/group
status of the specified group and all its links.
The result read from the internal context memory is stored in
Cmd_data00 through Cmd_data1F. Refer to RIPP Command Data
Registers for further details.
Read_delay
Adjust_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.
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 PM, 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.
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.
If sufficient links are not accepted, the group will not become operational. Note that within any
collection of links that are targeted to form an IMA group the group may not become
operational even though there are combinations of Prx links that meet the programmed
maximum DCB threshold. This would occur in situations where the internal algorithm used to
determine link order may not select the combination or “tightest” grouping of links that would
otherwise meet the programmed maximum DCB threshold. In this case, the relative delays of
the links are available to PM using the read_delay command. The microprocessor can then
analyze this information, remove the offending link or links and restart the group.
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2020889, Issue 2
73
PMC [ PMC-SIERRA, INC ]
