Motorola PowerQUICC II MPC8280 Series Reference Manual page 1281

links of the group. In order to determine if the GDS process completed
successfully, the ucode will set IGRSTATE[GDSS] to either of the following values
after the GDS interrupt has been generated:
— IGRSTATE[GDSS] = 00 - GDS process failed, a link lost IFSM SYNC during
GDS process
— IGRSTATE[GDSS] = 11 - GDS process completed
Software can then read IGRSTATE[GDSS] and use this status information before
deciding whether to change the links to the active state or to try and resynchronize
again at the group level. In addition to the above status information, the
ILRSTATE[ADD_NEW_M] bit of the link that caused the failure of the GDS
process will be flipped such that it is logically inverted with respect to the
ILRCNTL[ADD_NEW] bit. It is recommended however, that software, after GDS
failure and when restarting the GDS process, changes all of the links in the group to
the group unassigned state and then update the link and group parameters to their
default values before starting the GDS process again. Note that a link losing SYNC
during the GDS process can cause DCBO interrupt for other links in the group. If
this situation occurs, the GDS process should be restarted as described above.
5. IFSD (Link (IMA) Frame Synchronization Defect)—Indicates that the link has lost
synchronization (e.g., unexpected IFSN value for a number (GAMMA + 2) of
consecutive frames). If this condition persists, the link should be removed. The
threshold that would trigger the removal of the link is system specific. The IFSD
event corresponds to the "Loss of IMA Frame" (LIF) state and the software should
react to this by informing the FE (via the ICP cell, RxDefect = LIF) of the problem.
If the condition persists, IFSD events will continue to be generated every
GAMMA+2 frames. The MPC8280 maintains counters (if enabled) to track the
overall "quality" of a particular link: see OIF (Out of IMA Frame) and ICPVIOL
(ICP Violation) in Section 34.4.5.3, "IMA Link Receive Statistics Table." If the
link returns to working state, the MPC8280 will automatically perform Link Delay
Synchronization and generate an LDS event upon achieving synchronization. The
software can use one of the MPC8280 timers as a time stamp when handling IFSD
events and check if the "persistence" time threshold has been crossed when
subsequent events take place. The LIF state time stamp should be reset when the
IFSW event is reported.
6. IFSW (Link (IMA) Frame Synchronization Working)—Indicates that the link is
has achieved frame synchronization. This event is reported when a link has been
assigned to a group (start-up or link addition) or it was previously assigned and
working, but had a defect (see IFSD event). If going from defect to working, the
software should update the RxDefect field of the ICP. Again, a time stamp (timer)
can be used to measure the "persistence" time.
7. DSL (DCB Synchronization Lost)—Indicates that a link in a group with
IGRSTATE[GDSS] = 11 loses synchronization and enters the HUNT state at the
IFSM. When this interrupt occurs, the link should be removed by software, and the
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Chapter 34. Inverse Multiplexing for ATM (IMA)
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IMA Software Interface and Requirements
34-71