Motorola PowerQUICC II MPC8280 Series Reference Manual page 1264

IMA Programming Model
Table 34-27 describes the IDSR/IDMR bit fields.
Bits Name
0-3 GINTx Global Interrupt. Set when an event is sent to the corresponding interrupt queue.
4–5 INTOx Interrupt queue overflow. Set when an overflow condition occurs in the corresponding interrupt
queue. This occurs when the CP attempts to overwrite a valid interrupt entry..
6 INTO1/ INTO1: Interrupt queue overflow 1. See INTOx above.
GRLI GRLI: Global red-line interrupt. GRLI is set when a free buffer pool's RLI flag is set. The RLI
flag is also set in the free buffer pool's parameter table.
7 INTO0/ INTO0: Interrupt queue overflow 1. See INTOx above.
GBPB GBPB: Global buffer pool busy interrupt. GBPB is set when a free buffer pool's BUSY flag is
set. The BUSY flag is also set in the free buffer pool's parameter table.
34.4.9 APC Programming for IMA
Dynamically adding and dropping links from a group changes the overall bandwidth of the
group. The bandwidth of a particular ATM channel is programmed as a percentage of the
overall bandwidth, up to 100% in the case of APC pace of 1. In the case of IMA, it is
desirable to allow for the dynamic addition and deletion of links without changing the
bandwidth of individual ATM channels, so that ATM traffic contracts will not be violated.
To do this without requiring updates of the APC parameters of all of the ATM channels, the
APC algorithm must be modified to consider the number of links in the group.
To accomplish this for channels which will be used with IMA groups, the APC parameters
should be programmed to define the bandwidth of a channel as a percentage of one link of
the IMA group. As such, the APC pace can be greater than 100%, in the case that a channel
uses more bandwidth than a single link can provide. The APC pace will be scaled
automatically by the IMA group transmit parameter TNUMLINKS. After scaling, if the
pace required of the group is still greater than 100% of the group bandwidth, the channel
will be rescheduled at 100% of the group bandwidth. Refer to the examples in Table 34-28.
Table 34-28. Examples of APC Programming for IMA
Example
1 [The simplest case.] For an IMA group consisting of one 2Mbps link, with one CBR channel consuming the
full bandwidth of that link (i.e. 2Mbps), TNUMLINKS for the group should be programmed to 1 and the APC
pace of the channel should be programmed to 1 (PCR=1, PCR_Fraction=0).
2 Another 2Mbps link is added to the IMA group in Example 1. The overall bandwidth of the group is now
4Mbps. However, TNUMLINKS is now 2, and therefore the programmed PCR will be scaled by 2. [Note
that the scaling is done automatically internally; the PCR programmed into the channels transmit
connection table entry is not modified.] A scaled PCR of 2 indicates that the channel uses 50% of the
bandwidth of the group, or 2Mbps. Comparing to example 1 above, we see that the bandwidth of the
channel has not changed, even though the bandwidth of the group has changed.
34-54
Freescale Semiconductor, Inc.
Table 34-27. IDSR/IDMR Field Descriptions
MPC8280 PowerQUICC II Family Reference Manual
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