6.3 Programming Overrides
The following is a list of ways to override the default programming methods. The programmer should pay attention to these, because if done incorrectly, the PKTDMA may not function as expected and may be difficult to debug.
- Streaming I/F Overrides:
- flow_index. A value of 0xFFFF (or a value >= the number of RX Flows) will cause the RX DMA to use the channel (thread) number for flow_index. So, an RX Flow is always used, even if not directly specified.
- dest_qnum. A value of 0x1FFF is the normal, non-override value. When set to this, the RX DMA will use the RX_DEST_QNUM/QMGR fields in the defined RX Flow. Any other value will override the RX Flow value.
- Loopback Override: To loop TX descriptor payloads to the RX DMA (such as in Infrastructure transfers), set the SOURCE TAG – LO field in the descriptor to the RX flow number that should be used by the RX DMA. It will be passed through the Streaming I/F in the flow index parameter.