MPC8280 datasheet(1208/1386 Pages) FREESCALE

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Inverse Multiplexing for ATM (IMA)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

34-62

Freescale Semiconductor

3. Enable desired interrupts: ITINTMSK = x.

4. Software formats content of ICP template accordingly (see section “Transmit ICP Cell

Signalling”).

5. Program the Link’s ID (LID) in the IMA Link Transmit Table Entry (ILTTE): ILID = x.

6. Program the ICP offset (ILTTE): LICPOS = x.

7. Initialize the Transmit Queue pointers accordingly: ITQSP, ITQEP, ITQFP, and ITQXP.

8. Construct the new TX Group Order Table (includes the added/new link).

9. Point to new TX Group Order Table in the corresponding IMA Group Transmit Table Entry

(IGTTE): TGRPORDER = New Table Offset.

10. Configure this link/PHY as an IMA link in the IMA Root Table by setting the corresponding bit in

IMAPHY. See Table 34-3.

11. Enable the corresponding link/PHY in the IMA Root Table by setting the corresponding bit in

TXPHYEN. See Table 34-3.

12. Software must now wait for the corresponding FE link to go to “active” state (See

Section 34.4.4.1.4, “ICP Cell Templates.”). At this point, the link can be configured to “active

mode”, capable of sending data cells. Prior to this point, only filler and ICP cells were transmitted.

ILTCNTL[TXSC] = 1.

13. Increment the number of links currently in the group (IGTTE): TNUMLINKS += 1.

34.5.4.5

Link Removal Procedure

Removing a link from an existing group requires changes to both the group and link table entries. Aside

from the normal exchange of ICP cells by the state machines at the FE and NE, the following steps should

be followed. In general, a link entry is removed from the existing list of link table entries and the required

parameters initialized. Note that if only one link is used in a group the software must monitor the TC layer

in order to detect that this link has stalled.

34.5.4.5.1

Rx Steps

1. Formulate new group order table with the “dropped” link excluded (see Section 34.4.4.2.4,

“Receive Group Order Tables“).

2. 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 “IMA Group Receive Table

Entry”: IGRTE[STALL_THR] = x.

3. 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).

4. Indicate that the link should be dropped: ILRCNTL[RXSC] = 2.

5. 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).

6. Use the new group order table by inverting the current GOTP value: IGRCNTL[GOTP] = x.

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