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IXP400 Software
Access-Layer Components: DMA Access Driver (IxDmaAcc) API
April 2005 IXP400 Software Version 2.0 Programmer’s Guide
124 Document Number: 252539, Revision: 007
Upon completion of the DMA transfer, the NPE writes a message to the AQM-done queue. The
AQM dispatcher then calls the ixDmaAcc callback and the access layer calls the client callback.
Figure 45 shows the overall flow of the DMA transfer operation between the client, the access
layer, and the NPE.
8.9.1 DMA Initialization
Figure 46 and the following steps describe the DMA access-layer initialization:
Figure 45. IxDmaAcc Control Flow
IxDmaAccClient Task IxQMgr
NPE
1. ixDmaAccInit
2. ixDmaAccDmaTransfer
3. ixQMgrQWrite
4. IX_STATUS
7. ixDmaAccDoneCallback
8. Client Callback
6. WriteDoneFIFO
5. ReadReqFIFO
The NPE is triggered by a hardware event to
read a DMA transfer request descriptor.
A DMA transfer is performed and when the
transfer is completed the descriptor pointer is
passed on to the DMA Done Queue.
The descriptor contains the client callback
function pointer that is called when the
descriptor is passed back to IxDmaAcc (Steps
7 and 8)
B2359-03