Motorola PowerQUICC II MPC8280 Series Reference Manual page 1279

5. The "Stall Threshold" needs to be recalculated. This parameter defines the
acceptable tolerance to an emptied DCB condition (stalled link, see LS exception).
The recommended new value is: STALL_THR = 2 x RNUMLINKS x (3 +
RX_FIFO). See Section 34.4.4.2, "IMA Group Receive Table Entry":
IGRTE[STALL_THR] = x.
6. Start the delay compensation process for this link (in IMA Root Table) by setting
the corresponding bit in REF_LINK. See Table 34-3.
7. Software must now wait for the link delay synchronization process to complete. A
LDS (Link Delay Synchronized) exception will be generated by the MPC8280 as
soon as this happens.
8. It is now safe for the link to receive data, set link to "active" mode:
ILRCNTL[RXSC] = 01.
34.5.4.8 TRL On-the-Fly Change Procedure
Timing Reference Link (TRL) requests (CLAV) drive the distribution of cells to the
corresponding link transmit queues. To change the TRL, do the following:
1. Clear TRL bit for the existing TRL: ILTCNTL[TRL] = 0.
2. Set TRL bit for the new TRL: ILTCNTL[TRL] = 1.
Only one link must be selected as "TRL" in a group.
Note, when operating in IDCR mode (RX only), the timer value programmed was based on
the TRL Rate (TRLR) acquired when the group was brought up. It is necessary to restart
the entire group if the RX TRL is changed and a new TRLR (see Section 34.4.4.2, "IMA
Group Receive Table Entrye Entry") is expected.
34.5.4.9 Transmit Event Response Procedures
The following TX events may take place when operating in IMA mode. It is recommended
that all events be handled via an "exception/interrupt service routine" (ISR) as the response
time inherent with interrupt driven events should diminish the negative impact/propagation
of such events:
1. TQU (Transmit Queue Underrun)—Indicates that a transmit queue was emptied.
This implies that the offending link (PHY) is requesting cells at a faster rate relative
to the TRL. If the TRL is out of spec, then you will see multiple links reporting
TQUs (because all links in the group will be faster relative to the TRL). The
offending link should be removed (see Section 34.5.4.5, "Link Removal
Procedure"), check the following: PHY, TX Queue depth (start and end pointers
should not be the same), TNUMLINKS is equal (not less or greater) than the number
of active links.
MOTOROLA
Freescale Semiconductor, Inc.
Chapter 34. Inverse Multiplexing for ATM (IMA)
For More Information On This Product,
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IMA Software Interface and Requirements
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