PM7341 datasheet(103/413 Pages) PMC

103 / 413 page

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

105

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 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.

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..

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

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