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How long does it cost for the DMA to convert buffers? | Cypress Semiconductor

How long does it cost for the DMA to convert buffers?

Summary: 2 Replies, Latest post by qiang_qiang on 03 Apr 2015 07:36 AM PDT
Verified Answers: 1
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qiang_qiang's picture
User
7 posts

 Hello. Recently I'm reading an application note Designing a GPIF™ II Master Interface on http://www.cypress.com/?docID=47100.

On page 8 it says " The time taken for the DMA channel to switch to the next buffer is not deterministic, although it is typically of the order of a few microseconds. "

I tested the time mentioned above using FLAGA in the GPIF state machine, and found it related to the GPIF clock frequency, For example, if the frequency is 96MHz, the time is about 600ns. If the frequency is 12MHz, the time is about 2us, If the frequency is 375kHz, the time is about 38us.

So what factors are controlling the DMA to convert buffers? Which clock is driving this DMA behavior? Can we calculate the conversion time given a GPIF clock frequency?

Thank you!

ZengTotty's picture
Cypress Employee
2 posts

A socket takes a finite amount of time (up to a few microseconds) to switch from one DMA Descriptor to another after it fills or empties a DMA buffer.

If you have any further questions, please feel free to create a technical support case, our expert will be glad to help you

qiang_qiang's picture
User
7 posts

 I understand what you mean. Thank you!

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