Forum Discussion
New ContributorQuestions about the descriptors of the Modular Scatter - Gather DMA Core
Hi Derek,
@Derek_Teng wrote:In the Modular Scatter - Gather DMA Core, when I don't enable the Prefetcher Core, can I write multiple descriptors into the dispatcher FIFO through the Descriptor Agent Port at once? Then, by setting the Go bit in the Control Field of the last descriptor to 1 and starting the DMA transt input in sequence.
You are right.
Yours use case do not required the following prefetcher features, you can don't enable prefetcher.
With Prefetcher enabled, following features are supported:
- Descriptor linked list
- Data transfer to non-contiguous memory space
- Descriptor write back
- Hardware descriptor polling
- 64-bit address spaces
New ContributorHi Derek,
@Derek_Teng wrote:In the Modular Scatter - Gather DMA Core, when I don't enable the Prefetcher Core, can I write multiple descriptors into the dispatcher FIFO through the Descriptor Agent Port at once? Then, by setting the Go bit in the Control Field of the last descriptor to 1 and starting the DMA transt input in sequence.
You are right.
Yours use case do not required the following prefetcher features, you can don't enable prefetcher.
With Prefetcher enabled, following features are supported:
- Descriptor linked list
- Data transfer to non-contiguous memory space
- Descriptor write back
- Hardware descriptor polling
- 64-bit address spaces
New ContributorThank you for your reply.
I have another question regarding the Avalon-MM DMA IP core. The document "Arria ® 10 or Cyclone ® 10 GX Avalon ® Memory-Mapped (Avalon-MM) DMA Interface for PCI Express* Solutions User Guide" states that the DMA supports out-of-order completion.
This means that if I have 128 descriptors, the 128th descriptor may be completed before the 127th descriptor.
May I ask if I can turn off this out-of-order completion feature? I don't want it to complete the descriptors out of order. Instead, I hope it can complete each descriptor in sequence.
