DMA

[Ayaz]

Hi,

I have some questions regarding DMA:

1. What is Bandwidth Control, and what effect does it have on a DMA transfer?

2. What is Source/Destination Modulo? Could you provide an example of how to use it?

3. What are the Source Last Address Adjustments?

4. Is Source/Destination Signed Offset the number of bytes that need to be offset?

5. What effect does enabling the Source and Destination Offset provide?

[Julián_AragónM]

Hi @Ayaz,

1. Throttles the amount of bus bandwidth consumed by the eDMA. Generally, as the eDMA processes the minor loop, it continuously generates read/write sequences until the minor count is exhausted.

2. The Source Address Modulo (SMOD) defines a specific address range, which is the value after the SADDR + SOFF calculation is performed on the original register value. Setting this field makes it easy to implement a circular data queue in which the size of the queue is a power of 2.

For example.

• Assume a minor loop size = 4 = 4 NBYTES
• 
• 

3. At the completion of the major iteration count, the source last address value can be used to restore the source address to the initial value or adjust the address to reference the next data structure.

4. Yes, that is applied to the current destination address to form the next-state value as each destination write is completed.

5. Please refer to chapter 15.6.2.10 TCD Transfer Size Without Minor Loop Offsets for a continued explanation:

Also, I have sent you a private message through the community for a DMA training presentation.

Best regards,
Julián

[user_244572]

Hello Julian,
Can you send me the DMA training presentation as well ?
Thanks,

[Julián_AragónM]

Hi @user_244572,

I have also sent you a private message through community.

Best regards,
Julián

[malove]

Hello Jullian.
Can you send me the DMA presentation as well?

Best regards.

[Ayaz]

How can I clear the buffer and start refilling it after each major loop in the most efficient way?