Freescale Semiconductor MPC8260 - Manual (Page 1166)

Inverse Multiplexing for ATM (IMA)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
33-64 Freescale Semiconductor
• 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 PowerQUICC II,
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.
33.5.4.3.1 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.