Motorola PowerQUICC II MPC8280 Series Reference Manual page 1274

IMA Software Interface and Requirements
34.5.4.3.2 As Responder (RX)
The IMA GSM/LSM software will receive ICP cells in the ICP buffer conveying the state
of the FE's group and links. Once it has determined that the required minimum number of
links are available, it can proceed to enable the "group delay synchronization (GDS)"
mechanism in which the all links in the corresponding group are analyzed to find the one
with the shortest propagation delay. The amount of delay tolerated is programmable and is
programmed via the setting of the beginning and ending addresses (size) of the delay
compensation buffers (DCB). Note that the size of all DCBs must be the same and must be
initialized before the GDS mechanism is activated. Activate GDS:
• Set IGRSTATE[GDSS] to 1 (one) to enable GDS. Once GDS is enabled, the user
must not alter GDSS.
Once group delay synchronization is achieved, a "GDS" exception is generated. At this
point, ATM stream reconstruction can take place. In order for ATM stream reconstruction
to be performed by the MPC8280, the user must switch all links in the group to "active"
mode (i.e., capable of receiving data cells), as specified earlier in this section. The
initialization of the ATM TX and RX data structures required to generate and receive the
ATM stream is out of the scope of this document, however, it is documented in Chapter 31,
"ATM Controller and AAL0, AAL1, and AAL5."
34.5.4.4 Link Addition Procedure
Adding a link to 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 new link entry is appended to the existing
list of link table entries and the required parameters initialized. This has no impact until the
corresponding link is enabled via the PHYEN fields in the IMA root table.
34.5.4.4.1 Rx Steps
1. Reset all RX parameters in the new link table entry to zero.
2. Assign corresponding group number for the new link: ILRCNTL[IGNUM] = x.
3. Assign channel number for ICP cell reception: RICPCH = x.
4. Enable desired interrupts: IRINTMSK = x
5. Allow for the reception of ICP cells during the IFSM stage:
ILRCNTL[MON_ICP] = 1.
6. Indicate that this link has not yet been assigned to a group: ILRCNTL[GA] = 0.
7. Configure this link/PHY as an IMA link in the IMA Root Table by setting the
corresponding bit in IMAPHY. See Table 34-3.
8. Enable the corresponding link/PHY in the IMA Root Table by setting the
corresponding bit in RXPHYEN. See Table 34-3.
9. Software receives and accepts ICP cell values (e.g. M, LID, etc.).
34-64
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MPC8280 PowerQUICC II Family Reference Manual
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