MPC8280 datasheet(1205/1386 Pages) FREESCALE

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Inverse Multiplexing for ATM (IMA)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

34-59

•

Set the corresponding PHY bit in REF_LINK.

•

Set IGRSTATE[GDSS] to 1 (one) to enable GDS.

Once group delay synchronization is achieved, a “GDS” exception is generated. At this point, ATM stream

reconstruction can take place. In order for stream reconstruction to be performed by the MPC8280, the user

must switch all links and corresponding group (both directions) to “active” mode (i.e., capable of receiving

data cells). Set RX to “active” first, to avoid having the transmitter generate a data stream when the

opposite end is not ready:

•

Set ILRCNTL[RXSC] to 1 (one) to enable reception of data cells at the link level.

•

Set IGRCNTL[RXSC] to 1 (one) to enable reception of data cells at the group level.

•

Set ILTCNTL[TXSC] to 1 (one) to enable transmission of data cells at the link level.

•

Set IGTCNTL[TXSC] to 1 (one) to enable reception of data cells at the group level.

34.5.4.3.1

As Initiator (TX)

Most of the actions required when a system initiates the establishment of a group with X links involves the

exchange of ICP cells between the Near End (Initiator) and the Far End (Responder). In any case, both

ends must start with a group of X potential links configured to “filler mode”. One and only one of the links

in the group must be designated as TRL.

•

Set ILTCNTL[TXSC] to 0 (zero)—link is in filler mode.

•

Set IGTCNTL[TXSC] to 0 (zero)—group is in filler mode.

The actions at both ends mirror each other. That is, the Near End will initiate the establishment of a group

with X links by sending ICP cells to the FE and vise versa. The normal ICP state changes, driven by the

state machine software, are (on a per-link basis):

1. Not In Group

2. Unusable

3. Usable

4. Active

Refer to section “Transmit ICP Cell Signalling” for details on how to modify and transmit an updated ICP

cell.

It is the responsibility of the GSM/LSM (Group/Link State Machine software) to initialize the IMA ID (i.e.

group ID) in the ICP cell template and link ID in the corresponding TX IMA Link Transmit Table Entry

(ILTTE):

•

Set ILTTE[ILID] = corresponding Link ID.

•

Set IMA ID accordingly in the ICP Cell Template.

As an initiator, the NE (“end” is relative) must have established a group with X links provisioned.

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