Freescale Semiconductor MPC8260 - Manual (Page 1170)

Inverse Multiplexing for ATM (IMA)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
33-68 Freescale Semiconductor
8. Inhibit reception of cells over dropped link in the IMA Root Table: RXPHYEN &= ~x (i.e., clear
the corresponding link bit in the RXPHYEN entry). Note, you must reenable (set to 1) the
corresponding bit at a later point if you wish to use this link as a non-IMA link.
9. Software should wait (poll) for the PowerQUICC II to be using the new group order table. This
simply ensures that it is safe to modify/re-use the dropped link parameters (i.e., the
PowerQUICC II is no longer using the dropped link’s data structures). Do this by making sure the
group order pointer points to the new group order table (at this point, no more cells are extracted
out of the dropped link’s DCB), e.g.,: while (dcblink != new_pointer). DCBLINK is an entry in
the IGRTE.
10. Indicate that this link is no longer an IMA Link in the IMA Root Table: IMAPHY &= ~x (clear the
bit). Note, in a symmetrical operation, this step should be the last one performed (after both RX
and TX have been disabled). Setting this bit prematurely will halt transmission/reception on the
corresponding link.
33.5.4.5.2 TX Parameters
1. Formulate new group order table with the “dropped” link excluded (see Section 33.4.4.1.3,
“Transmit Group Order Table” ).
2. Point to new TX Group Order Table in the corresponding IMA Group Transmit Table Entry
(IGTTE): TGRPORDER = New Table Offset.
3. Decrement the number of links in the group (IGTTE): TNUMLINKS -= 1.
4. Inhibit transmission of cells over dropped link in the IMA Root Table: TXPHYEN &= ~x (i.e.,
clear the corresponding link bit in the TXPHYEN entry). Note, you must reenable (set to 1) the
corresponding bit at a later point if you wish to use this link as a non-IMA link.
5. Indicate that this link is no longer an IMA Link in the IMA Root Table: IMAPHY &= ~x (clear the
bit). Note, in symmetrical operation, this step should be the last one performed (after both RX and
TX have been disabled). Setting this bit prematurely will halt transmission/reception on the
corresponding link.
33.5.4.6 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 33.4.4.2.4,
“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 33.4.4.2, “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).