MPC8280 datasheet(1215/1386 Pages) FREESCALE

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Inverse Multiplexing for ATM (IMA)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

34-69

9. Program to appropriate rate and enable timer if using a BRG (refer to Chapter 17, “Baud-Rate

Generators (BRGs)”): TMRx, TRRx, and TGCRx. Note: This is only required if the IDCR clock

is supplied by the MPC8280. If an external source is used, this step can be skipped. An external

connection (physical) is required between the output of the BRG (TOUTx) and DREQx (see step

7 above).

10. Enable IDMAx interrupts (refer to Section 19.8.4, “IDMA Event Register (IDSR) and Mask

11. Clear IDCR table entries (reset to zero).

12. Issue the IDCR Initialization command (see Section 34.4.8.3, “IDCR_Init Command”). After this

point, the IDCR mechanism can be used.

34.5.4.12.2

Activating a Group in IDCR Mode

The following steps are required when activating a group in IDCR mode.

1. Configure the corresponding group to operate in IDCR mode: IGRCNTL[IDCR] = 1.

2. Indicate which is the last group that has IDCR enabled. Groups are numbered 0-7.

As additional

groups are created/added or removed, this field must also be modified accordingly with the group

number of the last group (in the order of 0-7) that has IDCR enabled. For example, lets say groups

0 and 1 are active and group 2 is being added. Then IMAROOT[IDCR_LAST] = 2.

3. After GDS has been achieved, the software can now read the captured TRLR value (see

IGRTE[TRLR]). At this point, the group’s corresponding IDCR Table Entry can be programmed.

IDCRCNT and IDCRREQ are both initialized to the integer part of: ((TRLR/(num_links x 128)) x

(2048/2049)). IDCRCNTF and IDCRREQF are both initialized to the fraction value of the

previous equation times 65536. For example, lets say ((TRLR/(num_links x 128)) x (2048/2049))

yielded 10.45, then IDCRCNT and IDCRREQ would equal 10. IDCRCNTF and IDCRREQF

would then be set to (.45 x 65536) = 29491 (0x7333).

4. Once the IDCR Table has been programmed, IDCR driven stream reconstruction for this group can

start: IMAROOT[IDCREN] |= x. The corresponding bit must be cleared if this group is being

deactivated/removed from a multi-group configuration.

34.5.4.13 End-to-End Channel Signalling Procedure

34.5.4.13.1

Transmit

The end-to-end channel signalling field can be used by software to signal to the far end. Because the

end-to-end channel is not covered by the SCCI field and there are no standard requirements for the

minimum number of frames between changes of the end-to-end channel field, it is not necessary to follow

the procedure for ICP cell signalling in order to do this; instead, the end-to-end channel field of the ICP

template currently in use can be directly updated. However, if a minimum number of frames between

changes is desired, then the procedure for ICP cell signalling can be used, skipping the step in which the

SCCI is updated.

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