Here you go: http://www.altera.com/support/examples/nios2/exm-scatter-gather-dma.html
There will be a new "Modular SGDMA" that will be posted up on the Nios II design examples page shortly. It doesn't use descriptor fetching and as a result is much easier to use in my opinion. If you want to take a look at it send me a message with your email address and I'll forward it to you. This is the Modular SGDMA feature list that isn't present in the SGDMA today:
- Up to 4GB transfer lengths
- ST-->MM early termination (packet length limiting)
- Interrupts per descriptor
- MM-->ST error signal
- Burst boundary re-alignment
- Park mode built into the descriptor (makes frame buffering easy)
- Descriptor sequence numbering (tag the descriptors then readback from the SGDMA to find out which descriptor the read and write masters are working on)
- Descriptor programmable burst
- Descriptor stride (address increment for fixed/interleaved data)
- Data widths up to 1024 bits
- Independent reads and writes (i.e. descriptors are dual buffered so the write master does not block the read master from starting up again)
- Burst lengths up to 1024 beats
- User selectable data/descriptor FIFO depths
-JCJB
