Freescale Semiconductor MPC8260 - Manual (Page 1165)

Inverse Multiplexing for ATM (IMA)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 33-63
of ICP cells requires that the corresponding PHYs (i.e., links) have been enabled and the corresponding
connection table entry/entries initialized (see RXPHYEN, IMAPHYEN, and RICPH). In “group
unassigned” mode, the first received ICP cell will always be reported to the corresponding channel’s buffer
(RICPCH) and subsequently every time there is a change in the SCCI (Status and Control Change
Indication) field of the ICP cell.
• Set ILRCNTL[GA] to 0 (zero).
Setting GA to zero (group unassigned) allows only ICP cells to be processed, all other cells are dropped.
The management software will analyze the ICP cells and program the corresponding IMA Link Receive
Table parameters:
• IMA Link ID (ILID)
• Link ICP offset (LICPOS)
• Select link as the Timing Reference Link (only one link can be TRL). ILRCNTL[TRL] = 1.
• Assign the link to a group. ILRCNTL[IGNUM] = x.
• Verify size of frame (M) is the expected value.
The software must have built in knowledge of the mapping between physical links and their corresponding
channel number (e.g., PHY 0 uses channel 2 (RICPH = 2)). Once a group has been established, the user
can have all links in a group report changed ICP cells to a single channel (either by changing RICPCH for
all the links to be the same or by clearing the MON_ICP bit):
• ILRCNTL[MON_ICP] = 0. Note, at least 1 link in the group must have this bit set.
33.5.4.3 Group Start-up Procedure
The IMA Frame Synchronization Mechanism (IFSM) is initiated when a link is switched to “group
assigned.” However, before that happens, management software must have programmed the group
parameters based upon the received/negotiated values in ICP cells:
• IMA ID (RIMAID)
• IMA Version (IMAVER)
• IMA Frame Size (RM)
There are other parameters that don’t depend on ICP information for programmability. Therefore, it is the
assumption that they have been initialized prior to the start of the IFSM. Start the IFSM by setting each
link in the group to “Group Assigned”:
• Set ILRCNTL[GA] to 1 (one).
Management software must now wait until each link in the group has achieved IMA frame
synchronization. For each link in the group that was “group assigned” an IFSW (IMA Frame
Synchronization Working) event is generated. See section “IMA Exceptions.”
Having achieved frame synchronization, software can now enable the Group Delay Synchronization
(GDS) mechanism (i.e., finding link with shortest delay and buffering accordingly via DCB).
• Configure group order table with the ascending link order (round robin distribution) to be used
when reconstructing the ATM stream.
• Set the corresponding PHY bit in REF_LINK.