Motorola PowerQUICC II MPC8280 Series Reference Manual page 1278

IMA Software Interface and Requirements
34.5.4.6 Link Receive Deactivation Procedure
The following procedure assumes that the link was part of the IMA group during the group
delay synchronization procedure and that an IFSW (IMA Frame Synchronization Working)
event has already been received for the link.
1. Formulate new group order table with the "dropped" link excluded (see
Section 34.4.4.2.4, "Receive Group Order Tables").
2. Decrement RNUMLINKS in the group receive table
3. 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.
4. Inhibit storing of cells in DCB for "dropped" link (in IMA Root Table):
REF_LINK &= ~x (i.e., clear the corresponding link bit in the REF_LINK entry).
5. Indicate that the link should be dropped: ILRCNTL[RXSC] = 2.
6. Software should wait (poll) for the MPC8280 to remove the link from the DCB
routine. The corresponding bit in the group table's LINK_DCB entry will be
cleared by the MPC8280 (IMA) (this means no more cells are being stored in the
DCB), e.g.,: while (LINK_DCB != REF_LINK).
7. Use the new group order table by inverting the current GOTP value:
IGRCNTL[GOTP] = x.
8. Set the link to filler mode ILRCNTL[RXSC] = 0
9. Initialize the DCB pointers accordingly: DCBSP=DCBFP, DCBRP=Null.
10. Initialize link DCB in external memory to zero.
34.5.4.7 Link Receive Reactivation Procedure
The following procedure assumes that the link was part of the IMA group during the group
delay synchronization procedure and that an IFSW(IMA Frame Synchronization Working)
event has already been received for the link.
1. Indicate that this is a new link (GDS/reconstruction function) by inverting the
current "add_new" bit value: ILRCNTL[ADD_NEW] = x.
2. Formulate new group order table with the new link included (see
Section 34.4.4.2.4, "Receive Group Order Tables").
3. Use the new group order table by inverting the current GOTP value:
IGRCNTL[GOTP] = x.
4. Increment RNUMLINKS in the group receive table.
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MPC8280 PowerQUICC II Family Reference Manual
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